Little to no rear brakes; proportioner valve delete?

[RalexS]

Recently purchased an 86 2wd auto TV, 118,000mi. Drove it to AZ state inspection facility to have it smog tested, they put it on the rear wheel spindles and then promptly told me they wouldn’t even test it because the rear brakes do not work. I brought it home, put the rear end on jack stands and sure enough, no rear brakes. I machined a little bracket to force the proportioner valve to be fully open all the time, it only slows down the rear wheels now. Manually adjusted and bled the rear brakes, still nothing. At this point I’ve got the proportioner valve 75% off, but the mounting bolts are just snapping. Has anyone used an aftermarket valve or successfully removed, cleaned, and reinstalled their own?

[Burntboot]

RS - I assume that we are actually talking about the LSP BV?

So Toyota put that thing in there for a reason (less load = less brake action = rear wheels not locking up and van wanting to swap ends)
Deleting the valve is a very bad idea, replacing the valve with anything other than what was designed, is also a very bad idea.

A good idea might be to figure out why it isn't working and correct as required.

~Perhaps your "modification" tipped the balance to less loaded?
~Perhaps the brake system has never been bled properly, note the bleeder on the load sensing valve.
-My guess is if you were to bleed that valve, you would have a significant quantity of disgustingness come out, things may improve after that.

~Perhaps it just needs adjusting.
~perhaps the van has been lifted?
~Perhaps the valve isn't at fault at all!?
(the rubber flex line to the rear axle could be swollen internally and not allowing fluid to pass.)

Without a proper diagnosis, its all just WAG's.

[Burntboot]

Sorry, missed the part where your mod improved action.

Sounds like there may be air in the system at the valve.

The van has 5 bleeders, bleeding process is in the manual, no one ever bleeds that valve and it gets full of crud, bleeding it should make a difference.

If you have good flow at the LSPBV bleeder and still nothing at the wheel cylinders, then the flex line becomes the next prime suspect.
(assuming of course there is no visible damage to the lines elsewhere (crushed/crimped))

[kamesama980]

I did delete the LSPV on my Toyota Pickup due to rust. Ran a manual prop valve and new lines from the master to every wheel. You can't delete just the valve, you have to rerun all the lines. Even with the manual valve run all the way down the balance was not ideal when empty, on a van or something with more rear weight it may be better. For liability and general prudence, I would not recommend it unless you're already an expert that doesn't need to ask about it on the internet lol. Improperly balanced brakes are NOT fun.

Keep in mind you have drum brakes back there, they must also be adjusted to work. They're only self-adjusting when clean and low rust. Does the parking brake work?

[RalexS]

Parking brake works fine and the drums do lock the wheels if I manually adjust them to be, I also bled all of the brakes and the lsp bv before I really started getting into it. If anything I’ll just buy a new LSP but they’re a little spendy so going to try and clean it first. Should have probably replaced the flex lines before ripping this thing out but they definitely look fine externally. Cleaning the valve out today but it’s going to be raining here for the next few days so I’ll probably reinstall this weekend.

[Burntboot]

So what happens when you bleed the brakes?

If the valve is causing the problem, you should be getting NO (or very little) fluid at the rear wheel cylinders.
Generally speaking an internally failed flex line will cause the brakes to slowly build pressure and end up being locked on, so not too likley

IF it were me and I were in your shoes, I would grab a helper and start looking for where the fluid is not getting to, starting at the back and moving forward.

The wild card here is I am assuming you are not getting fluid at the rear wheel cylinders.

If you are, then your problem is not hydraulic and you need to look at potential mechanical issues
Things like seized wheel cylinders, etc...,

[RalexS]

I am getting fluid at the rear brakes, I bled them until fresh fluid came through. They work, just not well enough to actually stop the rear wheels.

[Burntboot]

If you're getting a good strong stream I would be looking at the wheel cylinders and shoes for something seized/not moving.

If it was barely dribbling out, then it may well be back at the valve.

[RalexS]

I wouldn't say it was dribbling but it also wasn't as full a flow as I was expecting, I was using a hand pump vacuum bleeder.

[RalexS]

Got it apart; it was so corroded it had almost no action. Rust inside and out, cleaned it up really well and reassembled, it has nice smooth action now but I’m suspicious of the rubber seals. Also the internals were anodized green.. I have a hard time imagining that internal parts were anodized in the 80’s but I could be wrong- if I’m not wrong I feel like it must have been rebuilt but the bolts holding it on were so corroded that I have a hard time imagining it was ever removed, also. I can’t figure a way to test it so I’ll reinstall it this weekend and see what happens...

[Burntboot]

Nothing like having visual proof of why you need to flush your fluid every 2-3 years.

[RalexS]

Love to the non believers, it was definitely the brake proportioner valve! Passed inspection/emissions today. Excited to get to driving!