Bobzombie

Update... I put the new"reman" master on after blowing out all lines with air then fluid.
Brakes started to bleed down correctly!firmer pedal woohoo.
Then guess what happens??
the second "new" master takes a
the second piston(front) is flipping over the smaller seal
when compared to the oem seal its about half the size
so the moral is don't buy aftermarket masters they are junk

TNRabbit

You can get great quality brake parts from either Wab Fab or MarlinCrawler here on YotaTech.

Bobzombie

I am a parts guy at R&H Toyota So I can get parts at "good" prices, but it was a Sunday when I purchased the original master.

Bobzombie

off topic Rabbit, I have driven around alot down your way and have always noticed what appeared to be wheeling trails?!?! Is there a lot of places to ride down there? We usually come down at least a few times a year maybe we could meet up this spring

Cyclopsblown34

I woulda never guessed a junk rebuilt master cylinder. What a pain in the a$$.

TNRabbit

There is a place that is public accessible near Hollywood that is on the West side of Three Notch Road, I can't recall the name of the road. It's where high power lines run...

Bobzombie

TWO junk rebuilt master cylinders.

It just goes to show you that some things you can buy aftermarket and somethings you cant.
I had the same problem with the fuel pump. bought one, installed it,it worked for a week while I was working on the runner and then kaput.

Bobzombie

brand new toyota master cyl installed . Good fluid bleeding out, no air
pedal is pretty firm!
start it up lastnight pedal goes to the floor :???: driv3e it down the road
brakes grab really hard but no pedal it goes from squish to forehead in the steering wheel fast.?
So I decide to limp it to work this morning to have on of the techs here look at it (one of the old timers that worked on these off the showroom floor) :smile:
on the way the damn front freeze up again!!! The 3vze barely has enough power to move the truck on its own right ? much less with the damn front brakes applied! So i pull over and sit after about a minute I feel the brakes release. and we are off again but now I am afraid to use the brakes so I E-brake it all the way to work (scary)
So I am here safe and waiting to hear from my Tech buddy that need calipers
WOOHOO ALL NEW BRAKE SYSTEM

Cyclopsblown34

Sheesh, you've had a heck of a time with this one. At least you'll know your brakes are good up front.

Bobzombie

Well we have gotten to the bottom of this nightmare.
4 toyota techs later and the conclusion is....
Brake booster

Apparently the brake booster was vacumming the outer diaphram after applying the brakes which was causing the lock up, and causing the master to fail, the second piston in the master was being pressed beyond its limit and causing the pressure to be held and the fronts to stick and no fluid to come out of the bleeders and/or for the cup(seal) on the piston to invert which caused pressure loss and fluid to come out of the bleeders only when using a vacula or vacumme pump to bleed. With the outer diaphram vacummed out the inner diaphram push rod(pedal side) had a lot a free play between the master cyl push rod which is why the pedal felt the way it did.
It seems the that the stars aligned just perfectly for the issues to all react to each other and baffle us for so long. I would have never guessed the booster, in every car i have ever owned and everything I have been taught a booster failure would only lead to loss of brake assist.
So after new rotors and pads, shoes, flex lines, 3 masters, A flush, tons of fluid, hours upon hours of stress and headaches and now a new booster(getting installed today). My pig should be able to stop!!!

I hope this thread comes in handy! I wouldnt wish this nightmare on anyone.

Thanks to everyone who gave some input I greatly appreciate your help!!
Yotatechrs are #1

Bobzombie

4 days of perfect brakes....
today on my way in the front brakes lock up again. I forced it in to the closest parking lot (smoke rolling off brakes) cracked the bleeder loose freed the pads and E-brake it to work AGAIN :head pop:

The new Toyota master cyl is again. I can only assume that the master got messed up the last time it stuck when we found the booster to be causing the problem and after we unstuck the master. It probably got a tear in the cup(seal) on the piston and worked fine for a bit and then failed.

So I am waiting for another new toyota master to come in tomorrow.
I had the relay rod/tie rod/idler arm/alignment done today and I cant even drive it home.

I want a 96-00 Runner now!!! anybody got one cheap???

GSGALLANT

I've been following this thread, but have not posted yet, but I am amazed at how many times the problem seemed to have been fixed with different components, but then came back with the same symptoms. When your calipers seize, you said you crack the bleeder to push the pistons back in. When you crack the bleeder, is the fluid pressurized at all? Are you able to press the pistons in at all without cracking the bleeders? Are those the original calipers? Has the truck gotten regular brake fluid flushes?

It would be easy and cheap to rebuild the calipers with new seals (and replace any pitted pistons) to eliminate them as the problem. When I had problems with my calipers seizing on my '93, I found two badly pitted pistons in one caliper, and one badly pitted piston in the other caliper when I rebuilt them. When I bought the 4Runner, the brake fluid was visibly quite old, so it's no surprise that the pistons had pitted (brake fluid absorbs moisture readily from the atmosphere over time). Brake fluid flushes every two years are recommended.

As far as no fluid coming out of your bleeder screws (I don't think this is your problem, because I think I read that you successfully bled all 4 corners at one point or another), but I had a plugged bleeder screw on mine. I would push the pedal down with all my might, trying to figure out why I wasn't getting any fluid coming out of my open bleeder, and all it took to fix it was removing the bleeder and cleaning it out with a thin piece of wire and some compressed air.

For bleeding the system, I've seem many people damage the master cylinder using the pump-pump-hold method because they push the pedal down too far (further than it normally would travel). It is recommended to put a block of wood or something behind the pedal before you start bleeding to prevent this from happening. Even better, I made a bleeder tool that makes brake bleeding super easy to do by yourself. Details can be seen here. That tool will also work on your 2nd gen brake reservoir.

Sorry that's all I can offer at this time.

Bobzombie

I agree which is why this has been so difficult to figure out.
the true answer to this is yes when the front brakes are locked and I crack the bleeder there is pressure. as I stated before one time there would be good pressure and other times no pressure,it all depended on the issue with the master, it the front piston in the master was stuck and holding fluid the brakes would lock, if the piston was stuck and the seal(cup) was flipped there would be no pressure and the calipers would not apply(could move pads with fingers)
When the brakes are locked I can not push in the pistons with out cracking the bleeder loose. These calipers were on it when I got it the look old. The fluid was clearly very old and with much debris.
That is very true and we have used a "vacula" as Toyota recomends after the second master failed. This also follows along with the booster causing the masters to fail.

So at this point I put a new toyota master on it failed (wedged the front piston) we confirmed that the booster was the cause. We disassembled the toyota master, freed the front piston & looked over every thing. Reassembled,
bench bleed and the master is working fine. Replaced the booster put back on the master and bleed brakes(vacula) everything is fine.
4 days of driving and great braking. Then the master fails .
What is your thoughts on this last paragraph. forgetting everything else

Bobzombie

The front piston in the master is only supposed to go so far. Toyota recomends to vacuum bleed brakes so that the pistons in the master cyl dont get damaged due to traveling out of range. The end of the bore is not machined forpiston travel because it doesnt need to be The piston is not supposed to travel that far EVER.
However in my situation the booster continually applied pressure and pushed the piston beyond its limit. The last time we pulled the master off we could get fluid to squirt out of the rear port but not the front. We removed the snap ring and took the rear piston out and tried to push the front but it was stuck solid(wedged ) and would not move. We forced air in the front port and the front piston poped out.We examined it and didnt see any thing wrong. My guess is there might have been a burr on the piston or a tear in the cup which caused the piston to lock up again, locking up the front brakes again. Once I got it to work we put it up in the air and spun the front tires the brakes were still grabbing . The tech got in and applied the brakes (stood on the pedal, the pedal was very firm) and we spun the wheels again NO CHANGE.
This tells me the front piston in the master is stuck again.
After messin with the pedal a bit to see if it changed it went right to the floor and the brakes were no longer stuck. This tells me the piston freed up or cup flipped over which released the pressure
So I think the booster screwed up the toyo master and we freed it but the damage was already done and then today it failed.

Am I on track?? any other ideas?

Bobzombie

well I hope so. Thanks for everyones help. I guess we will see what tomorrow brings

Bobzombie

ok so we replaced the master today and everything seems to be good, SO FAR...
The other master front piston WAS stuck!!

Lets hope this is the last post in this thread!
Thanks for everyones help

GSGALLANT

Good to hear. Hope it stays good for you. This thread could be helpful to others... it wasn't a very common problem.

Bobzombie

I hope it does help some one, not that I want any one to go through what i did.
Its not common for a booster to do what mine did,well at least in my tech days thats not what happened when they failed.
Nothing pointed to the booster at all and I was busy chasing the master cyl problem.

Well its day two and everything is A OK !

Bobzombie

brake problems contagious around here? To the top to help others

dutchboy

Ok...i read this entire thread and the outcome sounded good. Hope it will help me? Can someone verify?
1990 4runner. 222,000 miles.
At various different times,under any driving conditions it will pull hard to one side or the other during braking. Normal braking and hard braking. At one stop light it wil pull hard right. As I continue to drive,and "stab" the brake pedal. It still pulls hard right. Then eventually it brakes evenly. Fine for awhile. Then it'll act up again. Sometimes the same hard pull to the right,other times to the left.
It has done this for about the past year.
This past summer I replaced the master cylinder,with a reman. Bench blead it...fine.
Blead the front brakes w/a friend,farthest first,(pump,pump,hold,bleed). Fine.
The next day. Pulling...one way or the other at various intervals.
A month ago,as I was driving to the shop,my dash idiot brake light came on. (and still comes on...then goes off...stays on 4 awhile....goes off...*sigh*). I replaced both front calipers and pads. Blead the calipers,fartest first...fine.
The next day...pulling.
2 weeks ago.Had it on the lift for exhaust replacement,and I inspected the rear brakes. They are fine. (6months old...wanted to have a look,as I had 2x's the parking brake didnt hold.Turn out to be road dirt/snow cinder in the drums.Cleaned,fine).
Till this day,it's still pulling.Primarily to the right.
All 4 corners bleed w/good pressure. Valves open easily after a day pre-soak w/ WD40. The brake idiot still remains in a non patterned on/off issue. I checked the switch at the end of the parking brake shaft. Good.
Does anyone think it's possible that my reman master is bad?
Besides the idiot light telling me something,somwhere is wrong...where would I begin?
My apologies for the lengthy post,but I wanted to be good w/my description.
Thanx all.
Dutch