Brake Battle -- Mushy-No brakes

[Bear80]

Ok this problem has been bugging me for over a year now and it seems to have gotten worse, which is a HUGE saftey factor on a DD and trail truck.

First let me say what I've changed:

New booster - didn't help, took it back and currently I have a booster off a '94 and the rod is properly adjusted.

New master cylinder - about the 3rd one, they all have been rebuilt asin units from autozone. (which I've put on other cars and trucks with no issues)

LSPV off a '94 - IMO it was like new, super clean outside, and the fluid was nice and clean that came out and what was in the master cylinder.

Rebuilt the rear slave cylinders - adjusted and checked SEVERAL times over.

New front rotors

And a few years back I put calipers off a '87 on, before I had any types of problems.

NONE of this had helped and the problem seems to have just started out of nowhere about a year ago.

The system has been power bleed at 30psi OVER 10 TIMES!! I've probably pumped 5 gallons through the system by now, if not more.

The Problem:
Now the pedel will just go to the floor when depressed firmly. Under light force the pedel almost feels "normal" and the truck stops "OK" which IMO is about 40% of the brakes power. Under sudden braking, the pedel goes to the floor and the truck brakes at the same or less 40% force.
It's really bad when I'm 'wheeling and stoped on a steep incline, or decline. I've also had the brakes not hold when they are wet and I'm stoped, or should I try trying to keep stoped on a steep incline. It prettly much feels like a bleeder is cracked open but I have no leaks anywhere and have never lost any fluid.

This all leads me to belive that the brakes - front calipers, rear cylinders are not getting enough fluid pressure to lock up. However there is only 2 things that I can think of that can cause this - air in the system or a bad master cylinder.

THE PEDEL WILL NOT PUMP UP. Only when the truck is off will the pedel go to the floor and then pump up, which is what the booster is suppose to do.

SOMEONE HELP!! I can't take this crap anymore, its unsafe like crazy and I just got my lift on and want to drive it again.

 

[foxfab]

Did you bench bleed the m/c? The m/c makes the pressure, so if there isnt enough pressure, it has to be either a bad m/c or air. Did you bleed the LSPV? In the future, I'd ditch it and get the manual valve kit from front range. It works much better.

 

[KliersLC]

What is your bleeding procedure?

Also, did ya bleed it at the MC?


You said it would pump up with the engine off. sounds like air that your non vaccum assisted foot cannot compress.

last and least likely, is the LSPV adjusted correctly?

Hope this helps.
Dan

EDIT, Damn you type fast!

 

[Bear80]

Common now, I do have a clue to what I'm doing. Bench bleed, power bleed, NO air period.

 

[foxfab]

I've had bad luck with those autozone POS m/c's. See if you can borrow a known working one?

 

[Bear80]

Ok, bench bleed, bleed at the lines for both the MC and LSVP. Could it be that even with my numerous and I mean numerous bleedings, could there have been an air bubble that worked into a critical location that prevents the brakes from getting pressure. Also could using my "power bleeder" at 30 psi not be enough?

 

[Bear80]

well the thing is I've had 3 autozone mc's on there now and it didn't make a bit of differnce. Also I had an autozone on there before the problem started and I've put autozone MC's on 3 other trucks with no problems.

 

[KliersLC]

Not trying to state the obvious, but some cars, (not sure if toyota is among them) use a different bleeding pattern because one side of the MC runs R/F and L/R, and the other side runs the remaining two wheels. If you bleed said systems in the conventional "start farthest from the MC approach" you will never get the air out. If yer using a bleeder ball that shouldn't be an issue. Do you have fluid inside the cab at the plunger??

 

[Bear80]

What I meant by the pumping up of the pedel was that the booster checks out fine. -With the engine off I depress the pedel (goes to the floor) then then next time the pedel stops about halfway up from the floor and holds pressure- that is the check for the booster, atleast by the book.

 

[Bear80]

no fluid leaks anywhere. Also I do the divers side rear first, passengers next, then front passengers, then drivers front, then LSVP. I also crack the lines at the LSVP since the only line that the bleeder valve is bleeding the front return line. I'v done this method on all my trucks, and the same with my dad's, never had a problem

 

[Bear80]

This is the way I've bleed the system over 10 times. Which each time is not in one setting, it's about a few weeks or days apart. Just depends on how pissed I get driving the truck. Sorry if I come off cocky but I'm just so fustrated with the problem and no shop wants to really help. They just say, oh lets bleed it for $50 first then start looking.....

 

[Bear80]

I've had bad luck with those autozone POS m/c's. See if you can borrow a known working one?

You know I thought that too, but advanced and most of the other retailers carry the same thing. Which it seems to me with so many of these trucks around and I'm sure by now they've had the MC changed that if the MC' they where selling sucked they would carry another brand. Also I would find that to be a HUGE legal liabilty to be selling faulty brake parts.

 

[KliersLC]

I always did Passenger rear first due to distance from MC, but this doesn' seem like it could come from that.

Check for the booster should be: engine off, depress pedal and hold. Start engine and it should push back a bit. Hmmm, maybe that was for hydroboost brakes...well worth a try anyway.

OK. Just checked operation in my 95 T100, yours should do THIS, not what I stated above. Pump pedal 3 times and hold pressure with engine off. start engine keeping pressure on pedal. you should feel a "bleed down" ie same pressure but pedal goes farther.

Good luck,
Dan

 

[Bear80]

yep thats the check I do for all my other trucks. And that's how my brakes worked before, but since the pedel goes to the floor when I start the engine, I just have to guess that booster is working. But as I said, I did get a new booster from advanced and it didn't make a difference.

 

[Bear80]

actually if you look at your brake lines, the rear drivers side is longer than the passengers side, so it is infact the longest distance from the MC

 

[KliersLC]

actually if you look at your brake lines, the rear drivers side is longer than the passengers side, so it is infact the longest distance from the MC

Never bothered

I read your post again, sure smells like master cylinder to me.

Draw a picture of your braking system, if you KNOW that a component is good, then cross it off.

Light bulb. Are 87 rotors as thick as 94s? could be reaching the end of their travel.....maybe......probly not. From what you have described, your master cylinder is the likely culprit.

Do you have ABS?????????

Good luck, I'll check back tomorrow
Dan

 

[Bear80]

Ooops, it's my '86 mini, so no abs. And the rotors are brand new, only the calipers are off an '87.

 

[Bear80]

Comeon, someone tell me I just need is to add water to my headlights....anything. This is driving me crazy, well mostly it's the damn reading I have to do for class right now........Think happy thoughts......I wish my brakes worked as good as my dad's 4runners' ......xmas on the beach.....

 

[zebrabeefj40]

I have seen air trapped in rear wheel cylinders that normal bleeding would not remove. The cylinders had to be pulled from the backing plates, turned 90 degrees to get the bleeders up and then bled. Then they could be put back onto the backing plate and rebled normally.

Do the brakes work better if you disconnect and plug the vacuum line from the motor to the booster? Any fluid in the vacuum line from the booster? Are you sure fluid is actually getting through the LSPV? Them things can be a real PITA SOB to get bled out too.

Good luck!
Nick

 

[Jukelemon]

Tell me how your are adjusting the rear drums.