Is my LSPV bad, brake lines clogged, or other? (2 Viewers)

[gyngbld]

I'm stuck and am hoping someone can tell me why my brakes are so bad on my new 1991 FJ80. Ive searched the Forums for hours without any success. When i press the pedal, 90% of the pedal travel nothing happens and the last little bit the pedal gets hard and I slow down (though not well). The booster has been replaced recently (PO) and the brake pads are basically new. I thought it was air in the lines so I began to bleed them and that led me here.

The two rears would not bleed. No brake fluid no matter how much I pumped the brake pedal. I followed the lines towards the engine and found this blue thing which i now know is a Load Sensing proportioning valve and know roughly what it is suppose to do. Both rear brake lines merge then go back to the top hole on the LSPV. Brake lines from the engine area go into the two holes on the left (labeled F, and w/ the arrow). When I used the bleeder on the right side of the LSPV it bled fine and lots of clear brake fluid shot out with every brake pedal movement. But when I unconnected the line on top going to the rears, almost nothing came out when I pumped the brakes. When I unconnected the brake lines to "F and the arrow" and again pumped the brakes, I noticed that the line going into F gushed and no fluid came out of the line that goes into the hole labeled with the arrow.....

Im no mechanic by any means, i bought this truck in part to learn (and who doesnt want an FJ!?!) so be patient with me if its a dumb issue with a simple solution. Is it normal for the brake line going into the hole with the arrow to not operate like the one below it? Could the "arrow" line be blocked and be keeping me from getting enough fluid to the drums / the air out of my system? If the bleeder works, why wont I get any fluid from the top hole? What would you recommend I try next? Any help would be appreciated. Thanks in advance.

If it helps, im the second owner and the truck has been sitting for months. Im fairly certain that almost everything except the shocks and the alternator and the booster are stock/original. No lift. Its a little hard to be sure but I think the brake line labeled "F" meets up with the brake lines that work the front brakes.

 

[Golgo13]

if you already have the brake lines open, it wouldn't hurt to test them.
There is also a rebuild kit available for that LSPV or, better yet, just get a new one.
When I got my '92, the brakes lines were rusted to hell and one of the hard lines even burst.
You can re-plumb the whole system with parts from the dealer pretty cheap. Only 1 of the longer hard lines is not available(that I know of). Everything else is available and not expensive.
I might have a line for the rear axle in my garage that can be yours for the cost of shipping.

 

[gyngbld]

I'll do what it takes , just trying to figure out what it takes and where to start. I appreciate the offer on for the line, if I go that route I'll definitely let you know. When you say "it wouldn't hurt to test them" how do I do that? I thought that was what the bleeder was for and it's working.

 

[flintknapper]

There is also a rebuild kit available for that LSPV or, better yet, just get a new one.

^^^^^ I'm not absolutely certain....but I think a 'new' valve is his only option. I don't there is a rebuild kit of any kind.

At least that is what I was told when I purchased mine.

 

[tacosupreme]

You could also get a proportioning valve and manually adjust rear brake pressure. Lifted rigs generally don't get enough fluid pressure to the rear. I zip tied my LSPV in the "high load" position,(closest to the body) but the rear do lock before the fronts on ice and that is not the right way to do it. Another thing to consider once you get that fixed is the condition of the rear drums and adjustment of the shoe. If you have to push 3/4 of the stroke to get them to touch, there is your problem.

Also it sounds like you are pumping the brakes with open lines. In that case as soon as you let up on the pedal air is sucking into the lines, and fluid won't come out.

Wilwood Brake Proportioning Valves 260-8419

 

[Malleus]

There's a kit with bushings, spring clip boot and pins, but not one for the valve. Your valve looks like it's in good shape. By the time they fail, the inside is gone and the outside looks like it's on its way.

If you're not getting fluid through the valve, you need to move the spool; it's a two position valve. With the spool in the inactive position, you only get fluid to the front brakes. Move the actuator rod so that the spool moves upward. This will open the rear galley.

You also need to do this when you bleed the system. It's not enough to bleed all four corners. You have to bleed the LSBPV once with the valve spool in both positions, then bleed the front corners; you may have some luck moving the valve between both positions while you open the bleed screw. A pressure bleeder is the only way to go. I like Motive's, but the choice is up to you.

You may still have air in the ABS system, which will require a short road trip on a gravel road. Then you'll have to bleed the system again.

HTH

 

[BILT4ME]

If you are not getting fluid out to the rear brakes when trying to bleed, it may be because the LSPV is set in the position to essentially stop all brake power to the rear, simulating a totally unloaded condition.

You need to adjust the arm UP in order to simulate a FULLY LOADED condition, which will allow maximum brake fluid flow to the rear. Then go through your complete bleeding sequence (LSPV, RR, LR, RF, LF, LSPV) Yes, LSPV is bled at least twice.

Double check the sequence with your FSM. If you don't have one, then follow this. it is typical.

 

[Malleus]

These also help:
Speed Bleeder Sizes (you want size SB1010 for the wheels; I think the LSBPV is SB8100)
Truck and SUV Application Guide - Speed Bleeders - Russell Performance Products

 

[Golgo13]

BRAKE TUBE & CLAMP. For 1991 Toyota Land Cruiser 4.0L | Toyota
maybe @beno knows actual availability for this stuff and what is in the kit. I just don't feel like looking it up now.

 

[nukegoat]

Remember if no hydraulics are actuating your rear calipers that youll have an abnormally hard pedal...

 

[gyngbld]

Thanks so much for everyone's input. It's really good stuff so far. I'll report back as soon as I can make the time to work on it some more.

 

[gummycarbs]

The only thing I see that looks remotely like any kind of rebuild kit is 04477-60010 "BUSH & BOOT KIT, LOAD SENSING SPRING":

I have no idea what the internals look like, but *maybe* those o-rings replace the ones in the valve. Oh, and that's an FZJ part. I remembered yours is an FJ80 after already typing this... Looks pretty similar, though.

Personally, I'd pull the bleeder screw and flush it with brake cleaner. One of my rear calipers wouldn't bleed and it was because of accumulated rust and/or disintegrating brake hose.

 

[flintknapper]

The only thing I see that looks remotely like any kind of rebuild kit is 04477-60010 "BUSH & BOOT KIT, LOAD SENSING SPRING":

I have no idea what the internals look like, but *maybe* those o-rings replace the ones in the valve. Oh, and that's an FZJ part. I remembered yours is an FJ80 after already typing this... Looks pretty similar, though.

Personally, I'd pull the bleeder screw and flush it with brake cleaner. One of my rear calipers wouldn't bleed and it was because of accumulated rust and/or disintegrating brake hose.

That is basically a hardware kit for the lever, it doesn't address the valve....and my understanding (per Cdan) is that the LSPV is not serviceable (internally). So I purchased a new one...when mine was discovered to be leaking.

 

[jonheld]

You don't have ABS on a 91 and you have drum rears.
There should always be some fluid pressure to the rear brakes regardless of the position of the LSPV. There's no position that is "front brakes only" unless the passages are clogged.
It's possible that the brake fluid is very old and full of crap and it has deposited a bunch of poop inside the valve. You can try to exercise the valve to free it up or you can take it apart on a bench and make sure the passages are clear. Or, just replace the thing.
I have also seen bleeders that are completely clogged and need to be cleared out in order to function properly, so don't trust old bleeders.

 

[Golgo13]

I don't know who of you saw the pictures of my LSPV, but I replaced it with a new part. Weird that you can rebuild the master cylinder, but not the LSPV. Oh well. Wish I would have realized what that kit was before I bought all the bits individually.

 

[gummycarbs]

That is basically a hardware kit for the lever, it doesn't address the valve....

Any idea what the o-rings are for? I've never taken any of it apart.

 

[chap79]

The O-rings are for the internal plunger.
As you can see here mine had corrosion internally which caused it to fail.

 

[gyngbld]

Update: I took the LSPV and soaked it in brake cleaner and noticed that I could not get the plunger to move up or down. I believe mine is also corroded inside and just needs to be replaced. I re-bled the system (still no fluid coming out of bleeders in the rear). Moved the bar that attaches to the LSPV to try to "trick" the truck Into thinking it's loaded heavy in the rear. And got ready to test drive it around my yard.

THIS IS THE IMPORTANT BIT, before I started the engine the pedal was hard, there seemed to be good pressure in the lines! I was excited up until I started the engine and the pedal fell to the floor..... No pressure; with the engine running I have no brakes. I can barely stop from idle speed. They are much worse than before.

BUT I noticed something else I think might be important. When the truck is idling, and I press on the brake, the RPMs drop slightly and it generally just doesn't idle as smoothly. Turn the engine off and I can build pressure in the pedal again.

Please tell me someone knows what would cause the pedal to have pressure when the engine is not running but have no pressure while the engine is running.

 

[gyngbld]

Update: I took the LSPV and soaked it in brake cleaner and noticed that I could not get the plunger to move up or down. I believe mine is also corroded inside and just needs to be replaced. I re-bled the system (still no fluid coming out of bleeders in the rear). Moved the bar that attaches to the LSPV to try to "trick" the truck Into thinking it's loaded heavy in the rear. And got ready to test drive it around my yard.

THIS IS THE IMPORTANT BIT, before I started the engine the pedal was hard, there seemed to be good pressure in the lines! I was excited up until I started the engine and the pedal fell to the floor..... No pressure; with the engine running I have no brakes. I can barely stop from idle speed. They are much worse than before.

BUT I noticed something else I think might be important. When the truck is idling, and I press on the brake, the RPMs drop slightly and it generally just doesn't idle as smoothly. Turn the engine off and I can build pressure in the pedal again.

Please tell me someone knows what would cause the pedal to have pressure when the engine is not running but have no pressure while the engine is running.

View attachment 1619217

 

[chap79]

Have you checked your brake booster?