Is it the infamous hot soak......

[pastadog]

So I drove home from work last night (10 miles), got home turned the van off and went into the house to get ready to take the girlfriend to dinner....20 minutes or so).... As we get in the car and start it up, it would crank, start and then die. So, I start it and give it some gas and hold steady at 2-3k...... then it was ok.

What does that sound like it could be? I just took it to a mechanic friend of mine to go through it and it checked out great. Curious if it's the hot soak problem ive heard about and if so what is that and how do i cure it?

P.S. this is the first time it has happened.

[kcg795]

You could either replace the fuel pressure regulator for a 1989 Toyota Van regulator, or put up with it. I chose to just put up with it for now. Won't hurt anything. They, supposedly solved the hot soak issues in the 1989 models by using a higher pressure regulator.

[pastadog]

Oh, OK. So basically it's not hurting anything?

What is causing this and does my vans symptoms even sound like a hot soak problem or something else?

Thanks guys!

[timsrv]

It sounds like it. There is a sequence of events and certain conditions that lead up to hot soak. It's hard to accurately duplicate these conditions for testing, so chasing down and proving the problem can be difficult.

I will attempt to explain the issue as I understand it. Since the van is a mid-engine vehicle the engine compartment cannot be vented on top (smoke and noxious fumes in the passenger compartment isn't a good thing). So as a result the engine is sitting under a sealed metal dome. When you shut off the engine, since the cooling fan is run by the water pump, the coolant circulation and the air ventilation go away. Since heat rises it gets trapped there in the dome and cannot escape. If it's a hot day and/or if you've been driving it hard (like going up a steep hill or freeway driving) then there's even more heat getting trapped there. To complicate things, the fuel rail, injectors, pulsation damper, and FPR (Fuel Pressure Regulator) sit right above the exhaust manifold and are covered by the upper half of the intake manifold.

The extreme heat that's trapped there soaks into the fuel rail and depending on the quality of gasoline and the pressure in the rail, the gasoline may boil. The result is expansion and vaporization.......otherwise known as a vapor lock condition. Since there is still pressure in the fuel rail, the regulator will not allow more fuel into the rail until pressure is reduced. The only way vapor/pressure can escape is through the injectors (when you are trying to start). Of course vapor isn't dense like liquid, so there's not enough energy being delivered for your engine to start or run correctly. As the vapor/pressure escapes into the manifold new fuel trickles into the hot rail and immediately vaporizes. When vaporization occurs, volume increases exponentially (expansion) and that keeps the pressure up. This in turn prevents sufficient amounts of fuel from entering the rail. Once started, keeping the engine RPM's up helps because the injectors will vent vapor/pressure faster and allow more new gas to enter the rail. The faster the cool gas flows into the rail, the quicker the rail cools. Once the rail is cool enough to hold liquid gasoline the problem disappears and the van runs normal again.

Because this involves boiling and vaporization, there is a direct correlation between the quality of gasoline and this problem. Back in the 80s this wasn't such an issue because gasoline had a higher boiling temp. Todays gasoline has lots of additives (such as ethanol) and this can significantly lower the boiling point. You can minimize this problem by staying away from the gas that says it has a high percentage of alcohol/ethanol but this option may not be available. It's my belief that gasoline is becoming standardized and brand name doesn't matter much anymore.

So this leaves you 2 other options:

1. Increase fuel pressure in the fuel rail (higher pressure = higher boiling temp)

2. Provide ventilation to your engine compartment after shut-down

I'm not crazy about option #1 because increased pressure = more stress on injectors and other fuel system components (IMO this is more of a safety issue). If and when a fuel system leak occurs, more fuel will leak and your fire danger goes up. That being said, there is an easy way to automatically increase your fuel pressure for only a couple of minutes after start-up. IMO, the benefit of this is questionable because you will only be increasing pressure AFTER the fuel has been boiled. In other words this will minimize the effects of hot soak, but will not prevent it from happening.

There is also a way to permanently increase pressure in the fuel rail, and this makes more sense to me because it's more likely to prevent the problem from occurring. Of course this benefit is off-set by decreased safety.......and that's not to be taken lightly. Fuel leaks in the fuel rail area are not uncommon and several vans have gone up in smoke (sometimes taking other property with them).

Before changes are made, one should understand how the system works. Our FPRs (Fuel Pressure Regulators) have 2 output pressures. When vacuum is applied to the FPR diaphragm it will put out around 30 psi. When no vacuum is present, it will put out around 40 psi. There is a temperature switch on the engine coolant filler neck (vans that came with factory AC). This is a simple on/off switch that's triggered by coolant temp. The switch is normally open but when coolant temp hits 230 deg F it closes and grounds the wire going to it. That wire is attached to the ECU (Electronic Controlled Unit). Each time the van is started, the ECU monitors that circuit and if it detects a ground condition it activates the EFI VSV (Electronic Fuel Injection Vacuum Switching Valve) for a period of about 2 minutes. When the EFI VSV is activated, it shuts off vacuum to the FPR and vents the FPR diaphragm to atmosphere. With no vacuum, the FPR holds pressure at around 40 psi. After about 2 minutes, the ECU turns off the EFI VSV, vacuum returns to the FPR, and pressure returns to around 30 psi.

The existence of this system tells me that Toyota realized the potential for heat soak, but miscalculated the activation temp (of course the changing fuel market is partly to blame). Later on when heat soak became a bigger issue Toyota issued a service bulletin (TSB #E020). Part of that bulletin requires mechanics to replace the 230 deg F switch with a much much lower temp 140 deg F switch. The lower temp switches were only available for this service bulletin campaign (see PDF file attached to this post) and are now NLA (No Longer Available).

If you think about it, the normal operating temp of the engine is about 185° - 210° F so this means the new switch will activate the "pressure up" mode of the fuel injection system almost every time the van is started (unless the van has had over an hr to cool). Because of this, I think it's reasonable to assume it wouldn't hurt for the "pressure up" mode to be activated on every start (including cold ones). This can be easily achieved by simply cutting the wire off of this sensor and attaching it to ground.

To permanently increase pressure, there are several ways this can be done, but probably the simplest method would be to disconnect the vacuum line from the FPR and plug it to prevent a vacuum leak. I wouldn't put a cap on the FPR port because you'd want the diaphragm in there to breath. Again, I don't recommend this, but I'm providing the info to help create a better understanding of these issues.

Personally, the remedy I like best is the "ventilation after shut-down" method. I'm using this method (and this method only) on my van and I've been happy with it. A side benefit to this ventilation is increased life span of rubber seals, rubber hoses, and other sensitive parts (due to reduced temps in the engine compartment). I've heard other guys talk about opening their hoods each time they stop or using computer fans and ducts to ventilate small amounts of cool air into this area, and I don't disagree with the success of such methods, but who wants to have a super heated and/or smelly cabin on a hot day? As for the small fans and ducts, there's already limited space here and access to key areas is already tough enough. That's why I chose to install electric cooling fans on my radiator. I built a shroud and installed (2) 10" high output electric fans on the back-side (engine side) of my radiator. I rigged them up to be thermostatically controlled and wired direct to the battery (so they have power all the time). I got an adjustable t-stat with a submersible probe, put the probe into the extra 16mm port near the front of the head, and set the t-stat to come on at 200 deg F. Now whenever the coolant temp is 200 deg F or above, the fans will run (doesn't matter if the ignition is on or off). This has worked out great for me and completely solved the heat soak issue.

The fans do come on and run (on and off for about 20 - 30 min after shut down), but they eventually stop and I've always been able to restart the van easily.

I just realized this is a pretty long winded post so I'll stop here. If anybody is interested in pictures or more details, please ask and I'll be happy to answer questions and/or post pics/schematics. Tim

PS: Installing an 89 FPR will help, but only slightly. I probably wouldn't replace an earlier version just for this benefit, but if it needed replacement anyhow, I'd definitely go with the 89 FPR. FWIW, normal operating pressure of the earlier FPR's is 27-31 psi and the "pressure-up" mode is 33-38 psi. 89 FPR's normal operating pressure is 30-33 psi & "pressure-up" mode is 38-44 psi.

This thread has a bit more related information: http://www.toyotavantech.com/forum/showthread.php?1582-What-does-a-particular-VSV-do-See-excellent-attached-diagram

[pastadog]

WOW...... Now that was a response!!! :clap:

Very very useful info Tim and definitely helped me understand what "heat soak" is. However, one last question.... Can "heat soak" hurt your engine?

It has only happened once and I run 91 octane from either chevron or shell.

Thanks as always guys!:drunk:

[timsrv]

Lol, I'm surprised you made it through all that. Sometimes I get started and just can't stop :lol:. Heat soak is hard on your starter and embarrassing when witnessed by others......other than that it's just a nuisance. Over time, the excessive heat in the engine compartment will harden rubber and plastic parts. Tim

BTW, high octane gas won't help. If your engine doesn't ping on the 87 octane stuff, then more octane is just a waste of money.

[pastadog]

BTW, high octane gas won't help. If your engine doesn't ping on the 87 octane stuff, then more octane is just a waste of money.

Holy crap balls!! I thought I read somewhere that your van will run better and get better gas mileage on 91? Please tell me I haven't been wasting my money..... :doh:

[timsrv]

Octane ratings effect pre-detonation, which can be an issue on high performance engines.............but we're talking about boiling points here. So unless you've done something to effect compression ratios, 87 octane should be fine for your van. I'd be a little weary of the no-name discount gas..........especially if has ethanol. Usually they will display a sign that says 10% ethanol or whatever. If you can run it and have no problems, then fine. If however you get heat soak issues more on one gas then another I'd avoid the gas that gives you problems. I'd also monitor gas mileage and avoid fuel that consistently gives you poor MPGs. Tim

[pastadog]

Awesome, looks like im back to 87 :yes:

Thanks Tim!

[ARP]

hey, I've tried both the solutions that Tim "detailed". Grounding the temp sensor heloed a little but didn't completely solve the problem. Ventilation solved the problem. I kept the stock cooling fan and fan clutch and installed an additional fan on the front of the radiator and hooked up a thermostat probe to the (return) fuel line right above the fuel rail. Set the thermostat to activate the fan at a temperautre such that the fan does not run during engine operation (except under extreme conditions like very slow ascent or idling in very hot conditions) but kicks on after shut down when the temperature climbs in the engine compartment. This was a relatively simple modification and worked awesome:clap:

[Geodesiq]

If someone could post photos of the fan install I would appreciate it.

[ARP]

well I should really try to take some pictures - maybe next weekend?

[timsrv]

Here's a bunch of pics of my fan set-up. I plan on writing a detailed article but haven't gotten around to it yet.

The shroud is made of 22 ga galvanized sheet metal and soldered at the seams with 50/50 solder. It is made to perfectly fit (2) 10" electric fans.
http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/shroud-1.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/shroud3-1.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/shroud4-1.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/shroudcut-1.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/shroudfans-1.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/shroudfans1-1.jpg


The adjustable thermostat I'm using to make my fans turn off and on is a capillary type with a 1/4" sensor probe on the end. To make the transition from the 1/4" sensor to 16mm X 1.5 pitch threads (the size of the extra unused port), I purchased a brass adaptor at the local hardware store. It originally was 3/8"mpt on one end and 1/4" compression on the other (these are readily available). I also purchased a 16mm X 1.5 die and simply chased the slightly larger 3/8" threads to convert to metric. The larger size 3/8 pipe thread was almost too big to chase without turning in a lathe, but with a little effort and patience this can be done by hand with only a vice and hand threading tools. After chasing, the new metric threads are perfect. You cannot even tell it was ever a standard 3/8 pipe thread . See the t-stat and modified brass adaptor below:
http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/t-stat-1.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_8970-1.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_8968-1.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_8971-1.jpg

Here's some links to thermostats controls: http://www.amazon.com/Flex---lite-31149-Cooling-Temperature/dp/B000FKBQTE/ref=sr_1_6?ie=UTF8&qid=1323160624&sr=8-6 http://www.amazon.com/Flex---lite-31147-Adjustable-Temperature/dp/B00029J3ZW/ref=sr_1_1?ie=UTF8&qid=1323160624&sr=8-1

The one in the black box is basically the same thermostat but it has a relay and some diodes added. I like this one because the relay protects the t-stat. The other cool part is it gives you multiple options for triggering fans. One of the posts hooks to your AC and turns the fans on anytime you're running AC, another post is for a manual override switch on the dash. I have this control installed on one of my vans and it's easier and cleaner than building one from individual components.

I see that Flex-A-Lite now has a variable speed fan control that uses a thermistor type probe with wires. It is a metal probe and could most likely be immersed in the coolant (most accurate way to trigger fans). Tim

[Harbilly]

Suddenly I have heat soak issues (vapour lock) on my 89 4wd. My experience with VW and Porsche tells me pressure has gone down in the fuel rail which allows the gas to boil. Given that 89 FPRs are higher pressure and somewhat free of this issue I am going to assume my FPR is bad. On the German cars the problem was almost always a bad fuel check valve (often part of the fuel pump). We had work arounds for Porsche 911s with their really high pressure and metal lines involving an in-line check valve unit (cheap) to avoid fuel pump replacement (costly). Do our vans have a check valve that might be the culprit or is it just the FPR that keeps the pressure up when the engine is off? I can open the engine hatch and bleed heat when I park etc but I think a new FPR is the way to go - right? Unless there is a check valve trick someone knows about?????

[timsrv]

Yes, it could be low fuel pressure, but it could also be the result of cheap gasoline. I'm not sure about where you're at, but in some places they introduce a "winter blend" gasoline around this time of year. This "winter blend" often has an even lower boiling point than the "summer" gasoline and could be at least partly to blame for your problem. I would recommend testing your fuel system with a pressure gauge before spending time and money on a fuel pressure regulator. FWIW, I have replaced the FPR on a 4wd van before and I can tell you that job really sucks. 2wd vans are manageable but the 4wd vans are very challenging. I'm a seasoned mechanic and I had to use about every trick and swear word in my vocabulary :(:.

Here's a write-up I just posted on Testing the fuel system / Replacing fuel pressure regulator (http://www.toyotavantech.com/forum/showthread.php?589-Testing-fuel-system-replacing-fuel-pressure-regulator&p=3289#post3289). Tim

[Harbilly]

Thanks Tim.
I guess this is just another darn job I should have done when I did the injectors and had the intake manifold off.
Man, I missed the boat on that one and left the hose of death, the TPS and the FPR untouched.
I deserve a beating!
Chevron Gas. Canada. West Coast near Bellingham Washington.

[foreverly]

Living in Texas, I'm looking to make my van Hot Soak proof. It seems an Electric Fan setup is the only reliable way & the extra cooling capabilities might help a bit during summer (which is year round here) too.

I did a general Google search & there are plenty of other classic vehicles that are struggling with modern ethanol gasoline too. Likewise, electric fan setups appear to be the standard practice.

Tim did a write-up on his thermostat set-up before but I've yet to see where & how y'all are putting your electric fans.

Tim did mention that the thermostats are a bit dodgy & need to be replaced every few years. Has anyone found an ultra reliable Thermostat?

Does anyone have any photos, part numbers, wiring diagrams, etc... I don't want to be the guy who can't start his vehicle on the Ferry this summer.

:wave1:

[timsrv]

I ran the set-up shown above for about 5 years & it worked great. The only bad part was this style thermostat seems to fail every 2 or 3 years. I had thermostat failure twice & both times resulted in an overheat :pissed: (before I realized what was happening and turned on the manual override switch). The 1st time it happened I thought it was a fluke, but the 2nd time really annoyed me so I replaced with a Flex-a-Lite #31165 variable speed control (http://www.amazon.com/Flex---lite-31165-Variable-Control/dp/B000CNN3LS/ref=sr_1_1?ie=UTF8&qid=1358223588&sr=8-1&keywords=flex-a-lite+31165+variable+speed+control). The thermistor sense probe used with this controller is also 1/4" diameter so it fits using the same adapter I used before. I was very happy with the performance of the variable speed control but my van was put out of commission by a reckless/uninsured/unlicensed motorist before I had a chance to test long term reliability.

I plan on fixing this van, so eventually it will be back on the road for more testing. Here's some pics of the installed Flex-a-Lite control:

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_2412_zps543b05e3.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_2402_zps41087d50.jpg

Although not directly related to the fan shroud/fans, here is another add-on/upgrade that helps direct air flow up and into the radiator/engine compartment when cruising. I made this "scoop" out of galvanized sheet metal flashing. There is a noticeable improvement in cooling when cruising at highway speeds with the AC on:

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_2365_zps86c795cd.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_2366_zps408649fe.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_2368_zps26f6b42a.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_2375_zpsc3c1e687.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_2376_zps1e578c72.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_2377_zpsdb89be3d.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_2378_zps4dd28c4d.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_2415_zpse0f8f23f.jpg

[Cirrus]

Hi Tim,
I am really interested in your awsome repair for the heat soak problem. After a hilarious scene at the local country club where I picked up my son, trying to restart on a hill with a car parked close to my front bumper, I had to back up the hill to get out. Spinning tires, a roaring engine, in lots of looks of disapproval had my son and I in stitches of laughter for a half hour after! But, I guess I need to see if I can cool the engine better so I'd like to create your setup. Did you make measurements or does it have to be a custom creation? This is my DD so I would need to turn it around fairly quickly. I would be happy to make a donation, etc, for plan's or guidance.
Thanks,
John

[timsrv]

The scoop was something I "threw" together in an afternoon with materials I already had on hand. I just cut it with tin-snips then bent it over itself for strength. Basically I just bent a little, held it up to the van, bent & cut some more, held it up to the van & repeated until I was satisfied. The shroud took more time as I soldered at the joints and used a heavier sheet metal. I didn't write down any dimensions, I just used an old radiator I had laying around and simply made the shroud to fit.

Any sheet metal shop could do this pretty quick. Just take them your radiator and print some pics from this thread for them. In hind sight I made mine more complicated than it needed to be. I wouldn't have had to make a relief for the transmission cooling hose if I had not made the shroud so deep. Trestlehed (member here) had one made that is thinner and simpler. I would guess it works as good as mine. He probably has pics posted somewhere. Tim

[Cirrus]

Thanks Tim,
found his thread and have all the part numbers etc.
J

[foreverly]

Cirrus - You may want to make note that Tim's set-up, while a good design in theory, left him with two blown engines. Its one of the first things he mentions in regards to the design.

I think when I finally install an electric fan I won't be removing the clutch fan. It is way too efficient at cooling the engine. Others have installed a smaller auxiliary fan, in addition to the clutch fan, to just deal with the hot soak. If the thermostat fails then you're not out an engine... you only have to deal with hot soak. I realize the clutch fans have their problems too & failed units have been the cause of many engine deaths as well.

Also, so you know, there are companies out there that will build you a shroud when you order the fan. I don't have any of this information collected at the moment but I know out in San Diego you can very easily find someone to take care of this for you if you don't have the tools, material, or motivation.

One last thing that I pondered, in regards to Tim's experience with his thermostats - I know there are units that hook-up into the radiator hose. Perhaps these thermostat's - while not as 'clean' in design - are more reliable. I'm not sure, but its something that I wondered.

Good luck, & let us know what you decide to do & inform us of the results.

[Cirrus]

Thanks Foreverly,
previous owner said cooling was not and issue and that seems to be the case so far, but my hot soak issue is bad. So far Ive settled on pumping the gas paddle 3 to 5 times and then try to start. Starts after 3 tries or so then I give throttle until it smooths out after a minute or so. I am having a hard time finding a mechanic who works on them but I PM'd Trestlehed to get his guy as we live very close to each other I think. I am going in for an oil change on Tuesday and will ask them too about adding a fan but I don't think they are very familiar with TV's. Also, I have to smog it so I am thinking of waiting until I see how I do at that first! I have my fingers crossed! Thanks for the heads up. I will search for the aux fan threads.
john

[foreverly]

John, you might want to read through some of the Hot Soak & Electric Fan threads over at TVP. If your hot soak is that bad you might want to try some of the other remedies until you get yourself a fan.

Instead of going to a regular mechanic you might want to find a classic car guy as Hot Soak is a problem on many late model vehicles. I helped my friend restore his 1943 Ford that his grandpa bought brand new. He had hot soak problems all the time with that car here in Austin.

Some of the coastal towns in TX have gas stations that stock ethanol free gas. Have you checked your area for ethanol free gas stations? There is a website out there that lists them all by state.

[timsrv]

Cirrus - You may want to make note that Tim's set-up, while a good design in theory, left him with two blown engines. Its one of the first things he mentions in regards to the design.....................

Who said anything about blowing engines? When my thermostats failed it did lead to overheat conditions (both times) but these were not severe overheats, just enough to get my attention, annoy me, and leave me with a confidence problem with the capillary style t-stat design. The flex-a-lite variable speed electronic t-stat I'm trying now gives me that "warm fuzzy" feeling, but only time will tell if it's going to last. That being said, foreverly's position does have merit. I go back & forth in my head when it comes to clutch fan vs electric. There are pros and cons to either way you go. A correctly functioning clutch fan will move more air at high RPMs, but the engine also works harder generating more heat while doing that. The beauty of the electric fan set-up is it will cool at maximum rate while your engine is at rest. To me that's the clincher that sells me on electric. Of course there's a down-side. An electric fan set-up will increase the load on an already fragile alternator.........and if the alternator fails.........battery goes dead quickly...........and no more electric fan.........or anything else (bad). It sucks when that happens.

Of course the other advantage to electric is it can be used to combat the heat soak issue (clutch cannot). If you aren't ready to give up your clutch fan, an alternative could be installing a pusher fan to the front of the radiator (or AC condenser if you have one of those in front of the radiator). The t-stat could be set up the same as mine or it could be put through the fins in the radiator. FWIW, initially I ran my t-stat by putting the probe in the radiator fins. It worked okay but I didn't like the response time. Heat transfer was delayed and performance was poor (thermostat would not consistently kick in until van was already running too hot). Submersing t-stat probe directly in the coolant was the answer. Direct contact with coolant gives instant response and fans come on predictably every time. Tim

[foreverly]

Thank you for correcting me. My memory is sometimes warm & fuzzy too, I apologize. :redface: For some reason I was in the understanding that you blew head gaskets before you realized the fans weren't working properly.

Thank you for the additional information regarding T-Stat placement.

[skibum]

I thought I'd comment on a work-around, if someone hasn't gotten around to upgrading the fans/cooling. I've experienced the hot-soak occasionally. When I feel that there is potential for the problem, I would let the starter run on for a couple of seconds more than a "normal" starting duration. There is the "intuitional" turn the key and quit when the engine starts, that you do every morning or after a considerable cool-down. By adding maybe a second or two, to that interval, with the starter assisiting in getting the fuel moving through has worked for me.

I'm citing this from memory, though, as I don't really seem to experience the issue much/at all any more. I'm not sure if it is coincidental, or not, but the problem seemed to clear up after I replaced the thermostat with an OEM Toyota thermostat (coolant, not fan control). I know I've heard Tim (and others) specify using that OEM thermostat and wonder if it is intended to help with this? It is constructed much differently than a Napa (or other) aftermarket thermostat.

Anyway, my $.02

[trestlehed]

Hey Cirrus, I just replied to your PM so check your inbox.
In the mean time, here is a thread concerning a "Cheap and Easy" heat-soak remedy.

Just prop your engine lid open after driving to vent the engine bay. Keeping the windows cracked about an inch or so is a good idea so when you get back to your van it's not an oven inside:

http://www.toyotavantech.com/forum/showthread.php?1042-Need-leads-on-finding-some-parts!

[foreverly]

Well that link goes to the thread about making the engine lid / seat holder out of bulk wire, but I think what we are all beating around the bush about is you may want to cut & ground the temp. switch wire.

Tim mentions it in his blog post (http://www.toyotavantech.com/forum/content.php?220-Hot-Soak) about hot soak. It is the switch that has one scrawny wire going to it below the radiator cap.

I haven't tried it - it may help a bit but from what I've gleaned its not going to fix the hot soak problem. I wish I could get my hands on one of those updated fuel pressure regulators though.

I was really hoping to hear from Arp on this thread. His posts at TVP indicate he has been through the gamut but in the end installed an aux. fan, keeping the clutch fan. I'm really curious about his setup.

Oh, I just found his contact info, but he sold his van...

[ARP]

ok I'm back by special request:rol:

I did sell my van with a fully functional hot soak fix which had been working nicely for about two years. I tried to keep it simple, kept the stock fan clutch setup and added a single pusher fan to the front of the radiator. Don't have the van or details but here's what I remember.

I went to the local Schucks (now O'Reilleys) and asked for a single aux. radiator fan of the correct size to fit on the front of the radiator (Thinline fan or something like that, there's not much room up there), and a thermostat kit to hook it up to. The adjustable thermostat unit had a metal probe maybe half the dimensions of a pencil which I zip-tied to a return fuel line right above the fuel rail (where I assumed the fuel vaporization ocurrs). Very simple, didn't submerge in coolant or anything like that. The fan had these attachments (rod like I think) that went through the radiator fins and a disk went over them on the other side and held the fan on. I attached the thermostat to the firewall right above the air element and hooked it up to unswitched power at the little + electrical connector box near the engine/air cleaner box (I believe there was a fuse in line here).

I set the adjustable thermostat so that it generally did not come on when the vehicle was operating (except once - see below). But usually, especially on hot days it would come on a few minutes after shutting the engine down as heat built up in the engine compartment. Depending on how hot the day/engine was it would cycle on and off for up to half an hour after engine shut down. I told people the elves were vacuuming in the van. Never had a problem with hot soak after this. Of course you need to make sure you keep a good battery in the vehicle with this set-up, although I never had a problem with that either.

Seriously, this was one of the easiest jobs I ever did on the van, only took a few hours I think (usually anything I did on the van stretched towards midnight if not the next day), and the results were spectacular. The hardest part was getting to the bolts holding the radiator on so I could rock it backwards and install the fan on the front of it (no need to remove it completely or disconnect hoses). I went through all the other ideas for a fix and all were unscuccessful until this one.

One advantage to this approach is you now have both kinds of cooling systems, if one fails you can fall back on the other at least temporarilly. My replacement vehicle (2004 Dodge Dakota crew cab) has both the fan clutch and aux. fan stock, though the needle has never strayed far from the 1/3rd spot :) and I've never heard the aux. fan come on. It may be overkill on this vehicle unless you're towing a load.

One summer after the fix I had a fully loaded van (for camping with the family) and the family, car top carrier the whole bit, pulling the grade out of Zion canyon in stop and go traffic, maybe 30 mph when moving. It was around 110 -115 F outside. AC full on. The worst possible conditions on Earth for overheating! My attention was riveted to the temperature guage. A few miles before the tunnel the needle got to 3/4's with the fan clutch already fully engaged, and I started sweating bullets. Then I heard the electric fan kick on and the guage maintained until we made it to safety (cooler temps) in the tunnel. I'm convinced the electric fan kept me from an overheat on that day.

Good luck Y'all!

[Cirrus]

Thanks to everyone who has replied on this thread......... ARP, thats sounds like a winner. I have an Oreillys right near work so I will pop in there tomorrow. I have AC so that may hamper things a bit but I am sure I will figure something out. Thanks again to everyone for pitching in with ideas. I will fully document what I do and post pics. etc.
Cirrus

[ARP]

I think I set the thermostat to trigger at 185 F, and that was real close to resulting in operation as described above. Each van might require a little different setting.

I had AC also but not rear air where I think there's a condensor on the front of the radiator? The front of my radiator was clear.

[foreverly]

Thank you Arp - this fix might be easier than the original TSB.

Cirrus - be sure to measure the gap before the radiator so you know how thick of a fan will fit in that space.

After a few other projects I'll be right behind you on this one, so let me know what fan & t-stat you end-up with.

[timsrv]

I started using my 86 van again after 13 years of it sitting in the black berries. I remember 1 or 2 times I had heat soak issues back in the 90's but nothing like now. As stated earlier I believe this is due to changes in the gasoline market over the past few years (lower boiling temperatures). Anyhow, even this time of year it's been giving me fits so I put my mind to finding a cure. I didn't want to spend a bunch of money and time with electric fans, shrouds, thermostats, etc so I came up with a compromise. I've been running/testing this for about a week now & it's been working flawlessly.

I had an old 11" electric fan laying around & decided to use it. I took my fan shroud off & took some measurements. I found there was more than enough room to install the fan directly to the engine side of the radiator so I put it there :dance2:.

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_2623_zpsd96bcb88.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_2628_zpsb0cf7a23.jpg

Since my intent is only to ventilate the engine compartment after shut down I don't need to worry about a custom shroud or a thermostat. I decided running the fan for 15 minutes after shut down would be sufficient, so I purchased a 12V "delay off" timer. The timer I chose was the Durite #0-740-57 (http://www.ebay.com/itm/230897587474?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649) programmed for 15 minutes. This relay was way overpriced, but I liked it due to the type of trigger it uses & because it fits into a standard Bosch relay harness. Coupled with a standard Bosch relay, a capacitor, & a diode I was able to construct a circuit that would activate the fan for 15 minutes every time the van engine is shut off (see PDF file attached to this post). Here's what it looks like:

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_2641_zps3583aa3b.jpg

Due to space and ease of installation I decided to put it behind the glove box. My van is pre-wired for an ice-maker but doesn't have one, so I'm using the ice maker harness to supply 12V ignition switched power source (this circuit is only activated when the key is in the "run" position). Also lot's of good places here to tap ground.

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_2645_zps167d086e.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_2644_zps0f7a46d3.jpg

I put the override switch down by my right knee. This switch will activate fan only when key is in "Run" position. I probably won't use this, but it might come in handy during the summer while I'm using my AC :thmbup:.

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_2646_zpseb4ff150.jpg

It's pretty cool to have this thing come on and go off based on time. My other van with the thermostat control will switch the fans on/off for about 20 min after shut down. I like the constant 15 minutes of fan much better than the on/off, on/off of the thermostat set-up, so now I'm thinking of adding this delay to my other van with the t-stat control. Tim

[foreverly]

Awesome Tim! :thmbup: I'm glad to see that you are experimenting with Aux fans. Where did that fan come from or where could one find a similar fan?

I think the override switch is a great idea. Does the switch have an 'off' setting too? There doesn't seem to be a reason to run the system during the winter. & even sometimes during the summer, I think I would want to have quiet moments.

[timsrv]

I didn't wire an off switch into the system but I also was thinking it would be nice. I had to move the van a couple times this weekend (just a few feet), but then the fan runs for 15 min. :doh:. It would be easy to do, but then easy to forget it's off. I may incorporate a temperature switch so it only activates when the engine compartment is over 200 deg. It's still awesome the way it is (compared to heat soak). I was experiencing start problems almost every time the van was warm. Since I put this in it hasn't happened once :thmbup:. Tim

[timsrv]

Where did that fan come from or where could one find a similar fan?

If I remember right I think I pulled it from something in a salvage yard years ago. Here's a similar one on eBay: http://www.ebay.com/itm/New-Turbo-Swirl-11-Electric-Fan-850-CFM-Puller-Pusher-No-Thermostat-/261176089730?pt=Motors_Car_Truck_Parts_Accessories&hash=item3ccf4edc82&vxp=mtr

[timsrv]

I did some research / cross referencing & came up with a temperature switch that activates (closes contacts) at 170 deg F. Since I have my thermal switch for the "pressure-up" disconnected & grounded, I'm going to put this switch into that port on my filler neck. The switch I found is AIRTEX Part # 1S4382. It has M16 X 1.5 threads (same as our sensor ports). Other numbers that came up in the cross reference are: 21595M4960, 21595M4961, 88923732, & SW542. I'm going to wire it in series with the ignition coil side of the timer so the 15 minutes of automatic fan will only occur after the ignition has been turned on/off & engine coolant temperature is above 170 deg F. It was a bit expensive, I found it on www.rockauto.com for $49.79. I suspect if I would have searched a bit more I could have done better. I'll post pics of it installed & report back on performance. Here's a file picture I found of the switch:


http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/getimage_zps8d39a3a5.jpg

[timsrv]

I installed the temperature switch tonight & wired it into the circuit. The over-ride switch will still work like before, but the automatic 15 minutes of fan after shut-down won't occur unless the coolant temperature is over 170 deg F. The only "hiccup" was the probe end of the switch was too big diameter to fit into the bore of the "pressure-up" switch. So I took the filler neck off and drilled the bore out to 1/2" and then it fit fine.

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_0944_zps7af3d62f.jpg

The bore was smaller for the old switch because Toyota uses the smaller bore to seal against the shoulder of the brass switch. Since this switch doesn't have a shoulder I'm using a copper crush washer to seal the new switch.

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_0949_zps29e817ef.jpg

Here's the switch after I've installed and wired it.

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_0954_zps660b2879.jpg

Here's the path I chose for the wire run. Note: To protect from chaffing I'm using a piece of pex tubing where the wire passes through the body.

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_0955_zps431c77fc.jpg

I wired this switch in series with the coil side of the timer relay. Here's a PDF file to show how the switch is wired into the timer circuit. Tim

[foreverly]

Very Cool. This is better than having an off switch.

But I love what would have made this impossible for me is just a little hiccup for you. Congratulations on sticking with your idea & seeing it through. :thmbup:

[holywolf]

Thanks to Tim for directing me here.

It is quite possible I have the hot soak on my newly acquired TV.

I am new to these vans.
The PO did replace the FPR but it still happened to me. So possibly could have been a bad replacement part or replacing the FPR won't help.

I will be paying more attention to the gasoline I use. I do not think concoco uses ethanol but I will double check.

What about using fuel treatment like sea foam or like products? Anyone attempt to saturate their fuel system with this to see if it helps?

[timsrv]

I have also installed an 89 FPR on my 86 van & it was not enough to make a noticeable difference. I also tried different brands of gasoline & that didn't seem to make much difference either. As a result I believe gasoline with a high boiling point is a thing of the past. Ventilating the engine compartment did the trick for me. To test yours, you may want to lift the engine access when making your stops during the day. If this eliminates your starting issues, then your problem is heat soak. Tim

PS: As a general rule I don't believe in, nor do I use automotive additives. Some may work, but I think most of them are a waste of money. Just my $.02.

[holywolf]

PS: As a general rule I don't believe in, nor do I use automotive additives. Some may work, but I think most of them are a waste of money. Just my $.02.

I agree for the most part. But sea foam works. I have seen it work in all my two stroke yard tools, motorcycles, and cars. In larger applications like vehicles I think it is more of a prevention thing than anything else. I have never done the carbon clean. I have had people put 2 stroke oil gas in some ATV's and motorcycles that really bogged them down. I put sea foam in the gas and it cleaned it right up. I also find that when I use seafoam in my tanks I getting a small amount better MPG. Not significant but that is not why I use it personally.

As far as most other products they are garbage. I posted a thread about BG products because I recently saw some amazing stuff happen when their products were used.

My buddy had a land rover disco. Infamous for leaking. BG make a coolant seal......yes I know they are terrible and can mess up your systems. I agree. However the BG stuff is made with an organic compound derived from a plant. When that compound hits air in the cooling system it seals it nice and tight. It is pretty amazing stuff. He has been driving with this stuff in his cooling system for 30k miles now. No issues. Instead of a 4k dollar fix it cost 10 dollars. I could not believe it. So now I always run their super cool in my jeep.

Those are the only "gimmicky" additives I endorse because I once was against them all until I saw results.

Hopeflly my TOYO OEM T-STAT replacement will help

This is a great thread!

[timsrv]

I know the cooling system stop leak products work, but as a mechanic I have also seen them plug-up radiators, heater cores, & make thermostats stick. These issues don't usually occur right away, they slowly take their toll (like hardening of the arteries). I don't have experience with the specific brand & formulation you mention, but suspect it would/could do the same.

As for the Seafoam, So far I'm keeping an open mind. In order to keep my master certified tech status I am required to regularly attend manufacturer sponsered seminars & troubleshooting clinics. It impresses me that Onan actually endorses Seafoam and recommends it's use to help de-carbonize their engines. I purchased a bottle of it a couple years back, but so far I haven't run into a carbon build-up issue serious enough to justify it's use/test it's effectiveness. Tim

[skibum]

I have been watching this thread for a while now, so thought I'd throw an idea out there. My buddy's dad ran a radiator shop many years ago (closed in the mid 80's) and one of his radiator leak solutions was black pepper. I've proved it out on a couple old Chevy pickups, as a workable solution. So, if you find yourself in the middle of nowhere with a leak, and a can of pepper, you can get back to civilization. :)

[holywolf]

I have been watching this thread for a while now, so thought I'd throw an idea out there. My buddy's dad ran a radiator shop many years ago (closed in the mid 80's) and one of his radiator leak solutions was black pepper. I've proved it out on a couple old Chevy pickups, as a workable solution. So, if you find yourself in the middle of nowhere with a leak, and a can of pepper, you can get back to civilization. :)

That's nutty!
Do you know the "science" behind doing this?

[skibum]

I don't know the science, but I would imagine that the pepper rushes toward the leak and clumps there. It's not a permanent solution, but it did work. I used to keep a can of pepper, a jug of antifreeze, maybe some power steering fluid up in the "trunk" area afforded by the roomy grill :).

[holywolf]

I know the cooling system stop leak products work, but as a mechanic I have also seen them plug-up radiators, heater cores, & make thermostats stick. These issues don't usually occur right away, they slowly take their toll (like hardening of the arteries). I don't have experience with the specific brand & formulation you mention, but suspect it would/could do the same


Yeah I have seen it too and steer people away.

The difference in the BG is it is an organic plant material and it does not clog up any systems and seals the holes.
At 30k miles and no system clogs I would say it is an advancement in quick stop products.

I used some and it worked for 10k miles on a vehicle without issue and then I sold the vehicle to a buddy and it still is not leaking.

It is David Blaine in a bottle!

[toytime]

Hi Tim, where / how exactly did you mount fan? Is it mounted to the water pump or to another pulley? I have an 87 AT not a 5 speed where do you recommend I mount fan, also I see your using a 3300 uf cap is there also a spec for the diode is it just controlling direction of current flow, and is it necessary to have the override switch with temp sensor thanks Ralph

[Harbilly]

Hi Tim, where / how exactly did you mount fan? Is it mounted to the water pump or to another pulley? I have an 87 AT not a 5 speed where do you recommend I mount fan, also I see your using a 3300 uf cap is there also a spec for the diode is it just controlling direction of current flow, and is it necessary to have the override switch with temp sensor thanks Ralph

Toytime:
I hung mine as a 'pusher' fan on the front of the rad years ago using the zip tie things that pull through a washer pressing against the fins that are sold exactly for this purpose. Years and no issues.
1986 AT 2wd
bill

[timsrv]

As shown on page 2 of this thread, I just mounted the fan to the radiator using THESE (http://www.amazon.com/gp/product/B000HE6H6K/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1). They poke through the radiator fins and hold the fan securely to it.

I'm not an electronics guy (no former training) I just experiment with stuff until I'm able to make it do what I want. A different size cap and/or diode might work better and/or last longer than what I used, but my method has been working well (I've been very happy with it). If/when I do this again I'll likely use a higher temp switch (like a 195 deg F), but the one I used is okay. Occasionally I'll need to start & move my van after the fan has already timed out, but the coolant temp is still above 170 deg, so the fan runs for another 15 minutes (unnecessary drain on the battery). Still, battery has never gone dead, just think it would be better with a 195 temp switch.

I never use the override switch, so in retrospect I would likely not install this if I do this again. Tim

[toytime]

:doh: Ok now I feel like an idiot I glanced over the pic's and thought you added the fan blade on the left mounted to the engine wow talk about a brain cloud thanks guys for setting me straight. Ralph

[SummerRose]

You all rock :thmbup:
I'm truly amazed :clap:

and also :dizzy:...
Alas! I am a lady... and would rather :doh: or :wall:myself repeatedly then attempt this job mainly because I feel it's likely very simple for someone who's done it already (or a mechanic) and would take me quite a bit longer to wrap my head around :cnfsd:.

That said, I'll be traveling most/if not all of our country for the next 6 mos. and would LOVE to pay someone to do this for me along my route...

Here is my likely route and dates when I'll be in each state UNTIL (then I'll be leaving the next day to go onto the next listed state):
Iowa FEBRUARY 1st
New Hampshire FEBRUARY 9th,
Nevada FEBRUARY 20th,
South Carolina FEBRUARY 27, (maybe)
Texas MARCH 1st,
Michigan MARCH 8th, (maybe)
Florida MARCH 15th,
Illinois MARCH 15th, (maybe)
Ohio MARCH 15th, (maybe)
New York APRIL 19th,
Pennsylvania APRIL 26th,
California JUNE 7th, then to
D.C. JUNE 14th, then back to to
Philadelphia until JULY 29th

:LOL2:

In the meantime I'm going to drive my van... when I stop, I'll lift my seat to let the heat escape... and see what happens when I get back in and try to start my van again.

Once I'm clear it's a hot soak issue, (which I'm near 100% certain it is) I'll look back here and hopefully have some offers with locations for someone (several someones??) to do the work and hopefully you'll be in the flow of my travels. I'd be happy to purchase the parts and deliver them to whatever address is best for "you" or buy them and keep them with me until I get to someone who is willing/able to get the job done...
TIM?
:drool:

On the other hand if "you" are confident anyone can do this... if you would kindly send me simple, concise, step by step instructions (cut and paste from all these scattered posts would work too), with step by step images (yes, I know I'm dreaming on that last one!) on how to do this myself... I'll do my best to make it happen or perhaps find someone local to make this happen. I'm good with putting computers together... and have worked on cars from time to time (change the starter/help my dad with plugs/etc.) so I just may be happy enough to tackle this myself if "you're" confident that I can do it.

Much appreciated!
And now that my head is exploding :yikes:I'll move on for now... :wave2:

Thanks!
Summer Rose

[SummerRose]

My mechanic who has been working on my van suggested I open the gas cap and let the heat escape that way...

Is that an easier fix then lifting my drivers seat or is he not understanding the issue?

Thanks again!

SR

[timsrv]

No, the place that needs to be cooler is the fuel rail (it's on the engine). Venting at the tank would have no positive effect. One thing you could also do (just temporary) would be to floor the throttle just as you turn it off. Let it begin to rev before turning off the key. The throttle being open causes vacuum to drop and this in-turn increases fuel pressure. This increased pressure (at the moment of shut down) will increase boiling temperature of the fuel in the rail. Tim

[SummerRose]

Got it. Thanx :)

Care to install a fan, etc. for me when on my travels?
:drool:

I understand if you're too busy... It's possible my mechanic will do it when I come back to Cali in May/June...

Thanks again!

[timsrv]

A few years back when the economy was dead I diversified for a while and one of those extra things I did was auto repair. Thankfully the RV business is booming again and I've got my hands full with that. So unfortunately this means no extra time for wrenching on cars (except for my own). Good luck. Tim

[kcg795]

By the air filter, there is a wire you can jump that'll cause the fuel pump to turn on. I was thinking about installing a time-delay relay to that. That way, when you turn the key to the "On" position, it'll run the fuel pump for a couple seconds. A lot of modern cars do this, but not our Vans. The fuel pump doesn't start running until you start cranking. It seems to make more sense to let the fuel pump run a cycle first so fresh, cool fuel can enter the lines and pressurize the system.

[dogger562]

Lol, I'm surprised you made it through all that. Sometimes I get started and just can't stop :lol:. Heat soak is hard on your starter and embarrassing when witnessed by others......other than that it's just a nuisance. Over time, the excessive heat in the engine compartment will harden rubber and plastic parts. Tim

BTW, high octane gas won't help. If your engine doesn't ping on the 87 octane stuff, then more octane is just a waste of money.
Three months later and I'm still with this problem, I've only had a couple of days to work on it dough, but it's starting to bug the heck out me. I've already checked fuel pressure and the EGR they seemed good. The one question I have is does "heat soak" happen over night because that's where my problem is at. Becouse everything is cold then gas, fuel rail, or would gas evaporated leaving air in rail? I also tried leaving engine cover/seat up all night just to see if that cured the problem, but it dint help. Any advice

[timsrv]

By definition heat soak is a problem created by heat. Problems encountered when cold are not heat soak related.

[dogger562]

Thank you, I can check this possibility off the list.

[Kyle]

I'm considering doing the conversion to a pair of side by side electric pull fans like Tim and others have done. The one detail I have reservations about is missing out on the variable speeds that the old mechanical fan turns at (i.e. slow/medium speed at normal temperatures and extra-fast when the engine's racing).

It seems like if an electric switch triggers the fans at normal operating coolant temperature near the filler neck (190? 200?) then it's cooling down the engine when it doesn't need max cooling. If it's set for "temp too high" then.. it's just lazy and not working for the van the rest of the time? Either way it would seem like it would just cycle the temp between too hot, too low then back up again. Am I wrong?

Is there a simple way to set this up (using only the one extra 16mm port with submerged thermo control) where one fan goes on for intermediate cooling and the second turns on for max cooling? Has anyone done this? I realize I could have two separate variable fan controls, but it seems messy and there's only that one extra port.

This just seems like a more practical way for the fans to operate and nicer than listening to two fans switch on and off at maximum speeds.

I've tried searching for things like "2 stage electric fan control" etc. with no luck. :dizzy:

[timsrv]

I'm using this one now: https://www.amazon.com/Flex---lite-31165-Variable-Control/dp/B000CNN3LS/ref=sr_1_1?ie=UTF8&qid=1333043290&sr=8-1. So far so good........here's a link that shows how I installed it:

https://www.toyotavantech.com/forum/showthread.php?491-Electric-fans-and-thermostats&p=9094#post9094

[Kyle]

I'm using this one now: https://www.amazon.com/Flex---lite-31165-Variable-Control/dp/B000CNN3LS/ref=sr_1_1?ie=UTF8&qid=1333043290&sr=8-1. So far so good........here's a link that shows how I installed it:

https://www.toyotavantech.com/forum/showthread.php?491-Electric-fans-and-thermostats&p=9094#post9094

Ah, thanks Tim, that's the thread I should've posted on!

That controller unit looks neat, I'm particularly interested in the cut-on at 60% speed feature. That kinda thing is what I was looking for, but you mentioned that you don't think it really matters?

Out of curiosity, did you run this setup on the same van you put the extra previa-heater-core-grill-radiator on?

[timsrv]

Ah, thanks Tim, that's the thread I should've posted on!

That controller unit looks neat, I'm particularly interested in the cut-on at 60% speed feature. That kinda thing is what I was looking for, but you mentioned that you don't think it really matters?

Out of curiosity, did you run this setup on the same van you put the extra previa-heater-core-grill-radiator on?

Yeah, I don't think it really matters. The reason being is running at 100% is just barely enough to keep up with the van's cooling needs (at least in the summer). In the winter there might be a slight advantage, but the power draw works out the same........only difference being a constant lower current draw vs a momentary full current draw. At the end of the day it's used the same amount of energy. I do think the variable speed controller is a bit more durable, but don't know that for sure (because I'm not currently using that van). And yes, it's the same van with the add-on Previa heater core.

There are pros & cons to whichever way you wish to go (clutch fan vs electric). Based on what I've done so far, I hate to say it, but I doubt I'd go through all this again as I don't think electric is any more effective at cooling. Regardless of which way you go, nothing I've done has completely solved the hot running issues. For 95% of the time both ways work fine. It's those super hot days when you're running the AC while stuck in traffic or climbing hills. With both methods I've still had to shut off the AC at times. Adding a single fan to a van with a working clutch fan is enough to keep the heat soak under control, but it is nice to have the extra room you get from deleting the clutch fan (and the oversize factory shroud). I guess the added benefit to electric is those fans can also be rigged to run after shut-down to help control heat soak. Tim

[Kyle]

There are pros & cons to whichever way you wish to go (clutch fan vs electric). Based on what I've done so far, I hate to say it, but I doubt I'd go through all this again as I don't think electric is any more effective at cooling. Regardless of which way you go, nothing I've done has completely solved the hot running issues. For 95% of the time both ways work fine. It's those super hot days when you're running the AC while stuck in traffic or climbing hills. With both methods I've still had to shut off the AC at times. Adding a single fan to a van with a working clutch fan is enough to keep the heat soak under control, but it is nice to have the extra room you get from deleting the clutch fan (and the oversize factory shroud). I guess the added benefit to electric is those fans can also be rigged to run after shut-down to help control heat soak. Tim

Ha, well that kinda puts the damper on my enthusiasm to go through with the swap. I want to get rid of heat soak, but also just give the van the most robust cooling system I can. That clutch fan fully engaged is pretty dang powerful.

Re: heat soak, another wacky idea I had was to put a little 12v (hot water rated) pump in the heater core coolant circut. If the pump was on a timed switch along with the blower motor I could just hit one button on the dash and the heater would dump heat out of the engine for 15min, or however long it's set for, while the engine's off.

I guess it'd be kinda annoying to have the heat on full blast in your car while you're in the store, and I don't know if it would actually even dump a significant amount of heat (esp. from the fuel rail area) to avert vapor lock.

Sometimes there's just too many options...

[Carbonized]

I was looking into electric fans last night, trying to find out the cfm. I found the Derale 16110 10" H.O. witch in Tim's set up would move 1600 cfm at 18.4 Amps. Then I realized that we have tried all sizes, single, dual with or without custom shrouds but I have yet to see someone bolting a 17inch directly to the plastic Toyota shroud 2 or 4WD.

Derale makes the 16917 an H.O. 17" (actual 16-7/8"), extremely low profile (2-5/8), dual speed Bosh motor, pumping out 2400 cfm at 23.5 Amps. At 16-7/8" it should drop right into our 17" shroud :thmbup:.

Flex a Lite does even better with their 118 flowing 2500cfm at a low 18.3 amps (same as the dual 10") but it's single speed and a little thicker at 3-3/16.

What ya think? :)

[timsrv]

You might consider an alternator upgrade before taxing it with a continuous ~20A. These Denso's are a bit fragile, otherwise I think it would be a great improvement. I look forward to seeing what you come up with. Tim

PS: There's a couple threads here were we talk about putting a Delco Remy CS-144 on the van. I've done it and in one place I posted a PDF drawing of the bracket and wiring mods required. Just search the site for "Delco Remy"

[Carbonized]

I was worried about that!
Is the dual fan set up on you welding van with the "mother of all alternator? with the bigger wires? and the relais here and controllers there....
Man, I don't know if I want to eat that elephant, even one piece at a time :lol: I'm a bit of a Sparky when it comes to electricity.
Plus any power gain from not running the fan belt has got to be negated by the big alternator, right?
Not to mention the clutch fan doesn't produce heat but the "bigternator" must make load of BTU ? Exactly what we don't want more of.
Too bad this 17" Derale looked pretty sleek for a while here.:yes:

[timsrv]

Energy is energy. Running the fan directly off of the front pulley has it's merits (simple, less likely to break). However it's dependent on engine RPM, so if/when you're overheating, you must also run the engine faster to effectively move air. Running the engine faster burns more fuel and creates more heat, so it's a bit of a catch 22.

Alternators can run hot, but I don't think we're talking anywhere near the BTUs of running the engine at 2,000 or more RPMs (required to move large volumes of air). Even if the alternator can't keep up at idle, if the battery is strong it will run the fans until RPMs come back up, so that's not a big deal either. Aside from being a relitively easy retrofit, the Delco Remy CS-144 is a strong and solid alternator. You can find used ones right out of the salvage yard that have factory output of 140A or more and are capable of surviving continuous duty in high heat/high output conditions.

All things considered, there are lots of variables to the way people use their vehicles and everybody has different preferences. A factory Denso alternator (new or rebuilt from Denso) isn't a terrible unit. They just get a bad rap due to all the questionable and/or poor quality aftermarket rebuilds. Factory Denso units will tolerate abuse to a point, but nothing to the extent a CS-144 will. Tim

[MyToy]

Tim:

As my 86 LE is being finished up and now will live and operate in Florida, my concern about Hot Soak has escalated.

With that in mind and April coming around the corner when temps here will really begin to climb I am making ready for a serious Hot Soak issue with my LE.

That being said and studying your detailed response with extra cooling added to the van for after engine off conditions gave me some thoughts.

This is quite a project and if needed I can do it but I thought of something else.

In your opinion, can an external air source (fan) drive air directly to the suspect area that is the cause for Hot Soak.

A similar model is used in piston aircraft by way of external electric fans moving lots of air through a Scat hose to the location in need for the extra amount of air. So my thought is to follow that model and add an external 12 volt squirrel cage fan located low under the ower steering reservoir and pumping air up into the fuel line area. I took your picture and guessed where the suspect area is.

This would eliminate the need to pull the fan out and build up the necessary mounts for the 2 new fans.

It can run on the same type of thermostat as you demonstrated here.

Any thoughts, or suggestions?

Thanks Tim
6739

[timsrv]

The fan set-up I'm using in post #34 is my daily driver and works well (doesn't require removing stock fan and/or building a shroud). I don't doubt your idea will work, it's just already cluttered in there. If you do that, try to direct the air to flow between the halves of the intake manifold (where the fuel rail and the injectors are). I'm always interested in new/different ways to solve problems, so if you go that way please keep us updated as to how it works out. Tim

[Carbonized]

I posted this on the subject; http://www.toyotavantech.com/forum/showthread.php?1841-Reworking-4wd-radiator&p=31776&viewfull=1#post31776 The thing I'm still questioning is: Do I blow fresh air in or do I pump hot air out? Witch way would be the most efficient? hummm....?

[timsrv]

If we're talking about a small but directed airflow, I would think pumping cool fresh air in would be more effective. If you move air out, that would do the same thing, but would initially be drawing air from other heated areas, thus reducing short term effectiveness (at least in the specific area of the fuel rail). Tim

[MyToy]

I was able to at least experiment with that. For sure blow in, not out. You will pull heat off the block first and will take some time to cool. By pushing, the block will not cool down any quicker but the suspected fuel line area will get the cool relief.

I will no doubt build a controller with some circuitry to switch this bad boy on and off. This tiny controller, as an example has 5 times more power than the entire EFI in the van (30 years later). So there are countless things we can do just by writing code.

I will try to get on the mechanical side of things by next month.


mt

[Carbonized]

Somehow in my head I keep seeing hot air relentlessly radiating upward from the mass of metal under the fuel rail and both ways at some point are making sense. It seems that, according to MyToy, aeronautic engineers prefer blowing in cool air, but fan makers clame more efficiency in extracting hot air :cnfsd: so the little voice keeps telling me: That hot air "pocket" has nowhere to go, if you take it away, cooler air will be drawn in its place, same as inside a paint spray booth or a sand blaster tank No? The contained environment makes it difficult to push things out. Interesting.....

With a bilge fan set up it would not be hard to figure out, flip the fan around and mesure temp drop directly on the fuel rail

[MyToy]

All good points and must be considered. There is however one other area that needs to be considered also. That is the level of sinking the heat (retaining it) within each component. Since we only need to reduce this temperature for short time period the time it takes to cool down the fuel components, ie fuel lines and such, are much smaller than the entire block of the engine. You are correct if we were planning on cooling the entire block, which would take 10 years with a push or a pull fan. But no, we only need a few minutes of cooling. The sinking power of the block verses fuel components is quite substantial. By blowing (pushing) cooler air hits these components at the same time, yet the fuel components will be effected the fastest and that is what is needed under these conditions. Early experiments somewhat proved this however until it is physically implemented anything can happen. Although heat rises, we are blowing so much cooler air over these components, we only need a small amount to satisfy the vapor lock. The right way to do this is with a temperature sensor on the fuel lines themselves set to some pre-deterimined temperature. This can be done digitally along with some timing numbers as per what Tim mentions on power up and power off. Here is where software is a good thing and can be done very accurately. After the initial tests, then measurements would have to be made to determine the correct numbers. Then it is the task of writing code that can satisfy it.

Not easy in the electronics but may be less disturbance to the engine area mechanically for the install.

Just some thoughts. Another month before my LE gets out of body and paint. Will start that process when she comes home.

My company owns its own Printed Circuit board machine that can do double layer boards. If I can get it to that level, we can store the file and make them on demand.

MT

[scotty]

If I wanted to wire a fan to run-on after turning the engine off, how would I connect it to a relay? Should I run power from the battery to both terminal 30 (which is usually constant power from the battery) and also to terminal 86 (which is usually switched power)?

[bikerjosh]

If I wanted to wire a fan to run-on after turning the engine off, how would I connect it to a relay? Should I run power from the battery to both terminal 30 (which is usually constant power from the battery) and also to terminal 86 (which is usually switched power)?

w/o the engine circulating coolant, what would this achieve? unless you were referring to the interior cabin fan?

Edit: oh never mind, guess i should read more than one post in a thread. :doh:

[hughdawgmmkay]

I started using my 86 van again after 13 years of it sitting in the black berries. I remember 1 or 2 times I had heat soak issues back in the 90's but nothing like now. As stated earlier I believe this is due to changes in the gasoline market over the past few years (lower boiling temperatures). Anyhow, even this time of year it's been giving me fits so I put my mind to finding a cure. I didn't want to spend a bunch of money and time with electric fans, shrouds, thermostats, etc so I came up with a compromise. I've been running/testing this for about a week now & it's been working flawlessly.

I had an old 11" electric fan laying around & decided to use it. I took my fan shroud off & took some measurements. I found there was more than enough room to install the fan directly to the engine side of the radiator so I put it there :dance2:.

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_2623_zpsd96bcb88.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/cooling%20system/IMG_2628_zpsb0cf7a23.jpg



Hi Tim - I found this thread while researching electric fan options to cool my van when sitting in traffic with my A/C on. I like this electric fan location the most, and wanted to reach out and see if you think this fan location is reasonable for a second fan while driving around.

My fan clutch is in great condition and keeps the van cool with the A/C off (and when driving with the A/C on) but my temps will creep to 201 F when A/C is on and I am sitting still in the GA heat.

Would you share your input on if this electric fan location would theoretically work for my use case, assuming I hooked up a pull fan. Any thoughts or concerns would be appreciated!

Thanks,
Hugh

[timsrv]

Hi Tim - I found this thread while researching electric fan options to cool my van when sitting in traffic with my A/C on. I like this electric fan location the most, and wanted to reach out and see if you think this fan location is reasonable for a second fan while driving around.

My fan clutch is in great condition and keeps the van cool with the A/C off (and when driving with the A/C on) but my temps will creep to 201 F when A/C is on and I am sitting still in the GA heat.

Would you share your input on if this electric fan location would theoretically work for my use case, assuming I hooked up a pull fan. Any thoughts or concerns would be appreciated!

Thanks,
Hugh


Hi Hugh,

Sorry I missed your post until now. The fan I put on this radiator was only to combat the heat soak issue. I have it set on a timer (shown earlier in this thread) that runs it for 15 minutes after the van is shut off. This ventilates the engine compartment and keeps the fuel from boiling in the rail (it works well). I also rigged it to a manual on/off switch so I could run it at other times. Although the fan works good for the heat-soak issue, it doesn't seem to help much (if at all) to combat overheating while stopped in traffic on a hot day with my AC on. I would recommend this set-up if you are having a heat soak issue, but don't expect it to help with overheating. Tim

PS: Experiencing overheating problems while sitting in traffic on a hot day with AC on is a pretty typical issue with these vans. If you find a solution to that please share as I'd be thrilled to be able to use my AC in those conditions :yes:.

[MyToy]

Hugh:

My hot sock issue may not be as bad as many but it did have some effect on the operation of the van. I am down here in Florida and mid day heat can get pretty intense. The engine runs very cool so there is no issue there but if I stop for 5 or 10 minutes the it restarts rough, where you have to feather the accelerator peddle for about a minute or so. Then it smooths out.

It did annoy me so I added a small timer and an extra air bypass valve to the system.
The high pressure sensor, which Tim recommends to ground at all times, is also tied to the same timer. I did that because when my high pressure sense wire is grounded it stays on for ever and should shut off in 2 minutes as per Tim's research. Mine didn't so I tied it to the same timer with the air valve. My guess is my computer may have an issue in that department.

I then calibrated the amount of idle increase I needed with both the high pressure active and the extra air valve to force the engine to maintain idle. I was going to use a sensor but Tim's timer idea really worked vey well for me also. It works flawlessly and is much less work. I have mine set for about 40 seconds. So for 40 seconds the idle, if no hot soak is in effect, idles a bit high, but only for 40 seconds.

In fact it worked so good I am considering building a small stepping motor drive to a motorized air valve and monitoring the tach where when the throttle control hits the idle stop the air valve adjusts itself to 800 RPM. This would mean you would intentionally set the idle screw in the mixture control unit to lower than normal idle and the air valve takes does the rest.

You may think of something yourself by knowing that the system has these dynamics. Again, the air bypass in this engine has all kinds of latitude to work with.

Think about it and have some fun.

MT

[hughdawgmmkay]

Hi Hugh,

Sorry I missed your post until now. The fan I put on this radiator was only to combat the heat soak issue. I have it set on a timer (shown earlier in this thread) that runs it for 15 minutes after the van is shut off. This ventilates the engine compartment and keeps the fuel from boiling in the rail (it works well). I also rigged it to a manual on/off switch so I could run it at other times. Although the fan works good for the heat-soak issue, it doesn't seem to help much (if at all) to combat overheating while stopped in traffic on a hot day with my AC on. I would recommend this set-up if you are having a heat soak issue, but don't expect it to help with overheating. Tim

PS: Experiencing overheating problems while sitting in traffic on a hot day with AC on is a pretty typical issue with these vans. If you find a solution to that please share as I'd be thrilled to be able to use my AC in those conditions :yes:.

Tim, just slowing down enough to get back to this myself. Thanks so much for the input! I braised together a shroud similar to yours, and am trying to figure out how I should use it. Hats off to you because I modeled mine after yours, with just a few slight tweaks.

Given your input and MT's down below, I am trying to think through scenarios on how effective this setup will be for me. Quick question for you, do you think I would be OK to use this fan setup, and still leave my stock fan clutch in place? My main concern is in restricting the flow & effectiveness of the fan clutch. Open to your thoughts!

9485

[hughdawgmmkay]

Hugh:

My hot sock issue may not be as bad as many but it did have some effect on the operation of the van. I am down here in Florida and mid day heat can get pretty intense. The engine runs very cool so there is no issue there but if I stop for 5 or 10 minutes the it restarts rough, where you have to feather the accelerator peddle for about a minute or so. Then it smooths out.

It did annoy me so I added a small timer and an extra air bypass valve to the system.
The high pressure sensor, which Tim recommends to ground at all times, is also tied to the same timer. I did that because when my high pressure sense wire is grounded it stays on for ever and should shut off in 2 minutes as per Tim's research. Mine didn't so I tied it to the same timer with the air valve. My guess is my computer may have an issue in that department.

I then calibrated the amount of idle increase I needed with both the high pressure active and the extra air valve to force the engine to maintain idle. I was going to use a sensor but Tim's timer idea really worked vey well for me also. It works flawlessly and is much less work. I have mine set for about 40 seconds. So for 40 seconds the idle, if no hot soak is in effect, idles a bit high, but only for 40 seconds.

In fact it worked so good I am considering building a small stepping motor drive to a motorized air valve and monitoring the tach where when the throttle control hits the idle stop the air valve adjusts itself to 800 RPM. This would mean you would intentionally set the idle screw in the mixture control unit to lower than normal idle and the air valve takes does the rest.

You may think of something yourself by knowing that the system has these dynamics. Again, the air bypass in this engine has all kinds of latitude to work with.

Think about it and have some fun.

MT

Great stuff, thanks so much! I'm going to have to think through all the options for a little while...I really like the timer idea you two have used.

I bought a little 'fuel pump' switch on Amazon (https://www.amazon.com/gp/product/B00OFRW32W/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) and have been considering making it a manual switch for when I determine I need to "ground" the high pressure sensor. I haven't been fully confident my computer would switch off the high pressure after 2 minutes either, so I've been considering this route.

More to think through, but really grateful for the input!

[timsrv]

Tim, just slowing down enough to get back to this myself. Thanks so much for the input! I braised together a shroud similar to yours, and am trying to figure out how I should use it. Hats off to you because I modeled mine after yours, with just a few slight tweaks.

Given your input and MT's down below, I am trying to think through scenarios on how effective this setup will be for me. Quick question for you, do you think I would be OK to use this fan setup, and still leave my stock fan clutch in place? My main concern is in restricting the flow & effectiveness of the fan clutch. Open to your thoughts!

9485

It looks nice but I'd worry about flow. I ran dual 10" high output fans on my cargo van (Post #13 in this thread) and although it worked okay I considered it barely adequate. The clutch fan will move a lot more air, but if you're planning on running it without the stock shroud I don't think it can do much (needs the factory shroud directing air flow through the radiator). Sometimes things will surprise you though. Since you've already got this much effort into it a little more experimenting wouldn't hurt. Good luck and let us know how it works out :thmbup:. Tim

[hughdawgmmkay]

It looks nice but I'd worry about flow. I ran dual 10" high output fans on my cargo van (Post #13 in this thread) and although it worked okay I considered it barely adequate. The clutch fan will move a lot more air, but if you're planning on running it without the stock shroud I don't think it can do much (needs the factory shroud directing air flow through the radiator). Sometimes things will surprise you though. Since you've already got this much effort into it a little more experimenting wouldn't hurt. Good luck and let us know how it works out :thmbup:. Tim

Thank you Tim! I will keep tinkering and get back to you all with what I land on!

-Hugh

[Carbonized]

I'm still, once in a while, tinkering in my head with the the remote bilge pump idea. So the other day I'm on this Porsche forum, here is this guy trying to cool the AC condenser with one of this:


http://forums.pelicanparts.com/uploads26/HP_486206_001_C7000_Fan_3_4_View1501505036.jpg

This thing makes my bilge blower look and feel like a toy :LOL2: , comes from a server where they line up 5 of them side by side. See how this guy uses it here:
http://forums.pelicanparts.com/porsche-911-technical-forum/964939-ac-air-bucket-design-build-rear-fender-condenser.html . Long read but had to binge it :lol:.
The best part is the price! So inexpensive he buys a bunch and doesn't hesitate to experiment and fry them! Pick up some cool air somewhere push it through some SCAT and blast it directly on fuel rail and injectors :thmbup:?

[trestlehed]

An idea I had a while back was to run a duct up the passenger side of the inner pillar next to/behind the passenger seat.
Have a small fan inside the snorkel duct, add your timer with relay. The big downside to this is you have to cut into the van body and subject your van to water leaks and rust. You would have to find an after market vent to mount to the the side of the van or even the roof if you are brave enough. Is that passenger side pillar kind of hollow like the drivers' side pillar where the ECU lives? If so, that might work for the vent.

A TVT member custom built a snorkel for 4x4 purposes (fjording rivers), maybe one of those could serve double duty by also venting the engine bay to mitigate "heat soak"?...

Option 3 would be to do the "rear heater delete", place your intake duct directly over the fuel rail area, then have your powerful bilge fan with relay dumping the hot air out the bottom of the van body behind the right front wheel. The rear heater delete might provide enough room for this.

Just some ideas...

[VanCo]

I've thought about taking a different approach. The fuel lines intimately snuggle the engine from one side to the other. Preheating the fuel with the engine block only makes sense from a 1980's comprehension of emissions standpoint. It is now known that cold fuel equals more power. More efficient power also makes less emissions. That's how we get cars with hundreds of horsepower that are EPA approved (that and corruption). I digress.

I'm thinking of running a new fuel supply line that connects to the factory hard line that goes to the filter. Run the line in front of the radiator to a fuel cooler then back to the fuel rail on the driver's side. All lines would be braided AN.

The problem I have is cavitation at the pump, in the tank. What happens is the fuel in the tank gets super heated from the return hose returning hot fuel continually while driving. When I park the pump can't get going because the fuel boils and causes cavitation.

If I'm going to do a ton of work, I want more power as a bonus.

[Carbonized]

[QUOTE=VanCo;41182 The problem I have is cavitation at the pump, in the tank. What happens is the fuel in the tank gets super heated from the return hose returning hot fuel continually while driving. When I park the pump can't get going because the fuel boils and causes cavitation.

If I'm going to do a ton of work, I want more power as a bonus.[/QUOTE]

What if you run the return line through the fuel cooler? You get a cooler tank = no pump cavitation = cooler fuel in the lines and injectors= more power, cleaner burn = less chances of hot soak :)>: No? I think that's what we ran in the Audi R10. Then again we where injecting at a gazillion PSI and inter cooling too!

[VanCo]

What if you run the return line through the fuel cooler?

I agree 100%; however, the supply line at that point would be easiest to manipulate for me. I may go full race van and reroute the supply and return for optimum cooling.

[Chardog1971]

It's been a while since I have been working on any of my vans. I don't have a good place to work on them out of the weather. I stopped driving the 89 4WD due to what I suspected to be the heat soak issue. That and the Ball joints. I have been parking on the street and moving it pretty frequently. I cruise around for a while to warm it up and keep the battery up to charge. I haven't had to re start it in a few years so, I forgot about that issue until I decided to fix the broken wiper.

I drove around a little and then pulled up to the shed to do the work. That is when I realized I wasn't close enough. Of course, it wouldn't start. Fired right up after lunch. Half hour or so. It was around 20 degrees f. so it cooled pretty quick. I know there is bad gas in the tank. I'm going out to drain it and start fresh.

After reading the last few posts, I'm wondering if the fuel pump heating up is the issue. I'm sure it hasn't been changed in years if at all. I suppose I'll try the opening the hatch after driving around for a while and see if that helps before I start adding fans, relays and whatever else is needed.

[Harbilly]

yes. The fan on the rad on our 1986 cargo is excellent for fighting heat sisk. Though, out of habit, we still park so we can drive forward once started - backing up sputtering is a nightmare. But the fan means we haven’t had a ‘fail to start’ since 2007.


Hi Hugh,

Sorry I missed your post until now. The fan I put on this radiator was only to combat the heat soak issue. I have it set on a timer (shown earlier in this thread) that runs it for 15 minutes after the van is shut off. This ventilates the engine compartment and keeps the fuel from boiling in the rail (it works well). I also rigged it to a manual on/off switch so I could run it at other times. Although the fan works good for the heat-soak issue, it doesn't seem to help much (if at all) to combat overheating while stopped in traffic on a hot day with my AC on. I would recommend this set-up if you are having a heat soak issue, but don't expect it to help with overheating. Tim

PS: Experiencing overheating problems while sitting in traffic on a hot day with AC on is a pretty typical issue with these vans. If you find a solution to that please share as I'd be thrilled to be able to use my AC in those conditions :yes:.

[89van]

Hey folks, apologies for a necro, but I saw this video recently and this got me thinking: is it viable? or am I out of tune for this idea...

Obviously, having the fuel rail hugging the engine is not ideal, but would this be a sort of band-aid fix or a viable option?

a Vapor Separator Fuel Filter. I will say, the guy in the video only mentioned it on carbureted vehicles however... dirtbikes, outboard engines, carburetors, maybe i'm missing the point entirely with it only being on carbureted engines unless it was used on a fuel-injected engine... :confused: Pressure differences between carb'd and EFI maybe? Not too sure, haven't thunk on it quite much but an interesting topic for an issue, and one that's now around the corner now that summer is here

Video link for reference: HERE (https://www.youtube.com/watch?v=-t6geNGbEXM)