1984 Van 2wd weak brakes

[Toyovan]

Quick back story to my van. I purchased my van back in 2021. First thing I noticed is how bad the brakes felt. The first 3/4 of pedal travel goes down easily with no resistance and makes a "decompression noise" the last 1/4 is when the braking starts but even then it doesn't feel convincing. The van feels more like it's "slowing down" vs "stopping" if that makes sense. Fast forward 3 years later over time I have changed front rotors, pads, calipers, rear shoes, drums and cylinders. Every brake hose and brake master cylinder. I have bled the system dozen of times, bench bled the master cylinder. There's no air in the system. I even bled the valve in the bottom middle. I have done the test to see if the brake booster is good and it checks out (i know bad brake booster means hard pedal) as it's the only brake component I have not changed. I have adjusted the rear shoes. System has no leaks. The brakes feel absolutely the SAME from the first time I drove it before changing every part I have. Are the brakes for this van not that good to begin and I'm just overreacting or is there something else I'm missing?

[Jan-Willem]

I feel your pain, I am still fighting my brakes as well, I am convinced I still have a small bubble somewhere, which just does not want to bleed. (Brake pedal sinks a bit, but only when the van is loaded….) I used to own a couple of mitsubishi pajero’s that had the load sensing valve as well, and these too, were a pain to bleed.
but to answer your question, no your pedal should be hard, even with the engine running, and the brakes are just as good as other cars of that time, you should be able to lock up your wheels. And because of the short wheelbase and high seating position, the brakes should be good enough to get your face close to the windshield :wnk:
where i live, we have a (two) yearly safety inspection. They test the brake system on all 4 wheels, to see if left and right are equal. Do they have such test where you live? That would identify what wheel(s) are underperforming. In my case both of my rear wheels hardly had any stopping power ( but they bled just fine) I found I had a failure in my load sensing valve. I rechecked myself, not very accurately, or professionally, by braking hard on my gravel driveway. Before fixing it, only the fronts locked up, after the fix, all 4 did.
i do not expect a broken load sensing valve to cause a soft pedal, but it may make it impossible to bleed perhaps.

[llamavan]

Brakes should definitely not be like that.

Failing to bleed the LSPV (or a bad one) does cause exactly those symptoms. A re-bleed of that (after the other brakes, in order) would be my first suggestion.

HERE (https://www.toyotavantech.com/forum/showthread.php?127-Load-Sensing-Proportioning-Valve-and-Bypass-Valve) is the main thread on the topic.

Gwen

[timsrv]

Brakes should definitely not be like that.

Failing to bleed the LSPV (or a bad one) does cause exactly those symptoms. A re-bleed of that (after the other brakes, in order) would be my first suggestion.

HERE (https://www.toyotavantech.com/forum/showthread.php?127-Load-Sensing-Proportioning-Valve-and-Bypass-Valve) is the main thread on the topic.

Gwen

:wss:

1st off, if your brakes are not performing properly, don't drive it. If you need to drive it, don't. Get an UBER or something until they are fixed. Don't worry about saving money, fix it right. With your issue, if the normal bleeding doesn't rectify I would try disconnecting the proportioning valve rod from the rear axle and wire-tie it in the highest position, then bleed the rears again (don't forget to re-install after bleeding). If still not happy with performance, replace the master cylinder followed by another thorough bleeding (always a good idea to bench bleed the new master before stuffing it under the dash).

If the pedal is hard but the van doesn't want to stop, it's probably a friction problem. Shoes & pads can't do their jobs if they are contaminated with brake fluid and/or any kind of lubricant. If the pads or shoes have been exposed to any of that stuff don't mess around, just replace and thoroughly clean the rotors/drums with brake clean. If you have a leaky caliper or wheel cylinder, replace it (or just replace all of them). If your rotors/drums are worn, super shiny, scored, discolored or have surface cracks, replace those too. Always clean rotors and drums thoroughly with brake clean before trying to run them. New ones are coated with an oily preservative to prevent rust, so it's very important to remove all that before putting them into service. I'm indifferent to brands of calipers, wheel cylinders, rotors, drums, and master cylinders, but I insist on the highest quality pads & shoes. In my opinion, OEM pads and shoes are the best, but in most cases are now NLA. When my stash of OE brake parts is gone I will likely start using Rabestos or whatever else is considered the highest quality. I don't know much about ceramic vs semi-metallic, but since the OE were semi-metallic that's likely what I'll stay with. If you are not comfortable working on your brakes and/or you can't get them to perform correctly, pay a professional. Tim

[Toyovan]

Thanks for taking time on replying Tim. So in short, I have replaced every part that has to do with the brakes other than the brake booster and the proportioning valve. And when I say everything that includes calipers, pads, discs, lines, shoes cylinder, drums and the master cylinder. I bench bled the master cylinder, no air comes out of any of the lines including the valve. I got help from my cousin who has lots of experience as a mechanic. I bled the system more times than I can count including gravity bleeding. The brakes feel exactly as how I first got the van before installing all those new parts. The pedal doesn't feel hard. It feels spongy. No resistance the first 2/3 travel. Only the last 1/3 and still doesn't feel convincing. A while back i had someone else who's has the official title of professional technician in automotive and he mention the vacuum line that comes from the engine to the booster. He says when he disconnected it from the booster the idling didn't change. "It's supposed to be running rough when I disconnect it because it's a big vacuum leak" is what he said. Unfortunately he wasn't able to come back to check again and haven't had time to check that as I've moved on to working on other systems on the van for the moment. Can that be an issue that I should look into? I've also been told to check the pre load on the booster/master cylinder. I've recently learn about the proportioning valve. Is there a write up about doing what you said here on the forums? Thanks!

[timsrv]

Every person has a different expectation of how brakes should feel, but the bottom line is they need to work good enough to lock up on dry pavement. If the brakes are not capable of doing that, they are not working correctly. Based on what the other guy said, your booster sounds suspect. The way he checked it isn't the most accurate way to verify, but if it's a good indication there's a problem. Like he said, disconnecting the vacuum hose from it should create a vacuum leak big enough to make the engine stumble and/or die.

I would want to check it by trying to pull a vacuum on it and verify it can hold it. If you don't have a vacuum pump with a gauge, you can use the poor man method. Poor man method is to put a hose on it, then suck. Use your tongue between breaths to seal the hose. After a few good sucks, there should be enough vacuum in the line to pull your tongue tight against the tube opening. When you remove your tongue there should be a rush of air traveling back into the booster. FYI There is a diaphragm inside it. If it's ruptured you will not be able to pull a vacuum. That means it isn't doing it's job and due to the vacuum leak the van will run rough. Sometimes when there's vacuum leaks, instead of addressing the root problem, some people turn up the idle and/or make other adjustments to prevent the engine from dying (perhaps that's been done here). If the booster is bad you will likely need to turn down the idle again after it gets replaced. Tim

[Toyovan]

Wouldn't a bad booster means the brake pedal is hard? I did the booster test that's in the book (pumping and holding when off then turning on, something like that) and it checked out.

[timsrv]

Yes, the booster is there to make the brakes easier (vacuum assist/power brakes). They will still work with a bad booster, but will take a lot more effort to engage. I don't have much else to offer without driving and inspecting in person. If the don't function correctly then maybe it's time for a professional mechanic. Tim