Bad Master Cyl?

[CJM]

Been chasing this issue for awhile, if anyone recalls I adjusted the booster pushrod before and it seemed to cure it for awhile. Master appears to be stock toyota. I had a poor brake pedal and even worse pedal height that basically no matter how much you adjusted the rear shoes it didnt change. I finally gave up and adjusted the booster pushrod and everything seemed fine for about a month. Pedal worked fine, was much higher than before and stopped well.

Fast forward to the other day and I noticed again, hmm pedal is low but truck still stops...Adjusted the pushrod again and its better but not great (didnt want to over adjust it by mistake)it baffles me why I needed to adjust it again.

There is no hissing, the booster is holding air it seems. Truck off pump up the pedal it doesnt seem to sink. Truck on, pump up pedal and yea it does slightly sink. I can barely fit my foot under it, when before I know I could easily fit a my foot with workboot (much larger than my sneaker today) in the gap easily after I adjusted the pushrod.

I think the seals in the master are bad, whatcha think?

[CJM]

I think Im just gonna buy a master in the end, not much else in the system is old so its one of the few things I aint replaced. Maybe Corax can answer this: Can I use a non ABS master with an ABS truck? I cant see how they could really be different. Also going to upgrade to the 1 1/16" master b/c I want a firmer pedal period.

edit: nvm I found your post on TTORA Keith.

http://www.ttora.com/forum/showthread.php?t=144432

You said theres no difference. I hope the extra 1/16" isnt too firm, I know I have a dual diaphram booster for sure tho.

[CJM]

I could really use some advice guys. I know Im annoying with all my issues, but Im desperate at this point. I adjusted the pushrod the pedal went down again by today, its been less than a week.

There are no external leaks at the master, either at the seals or at the fittings either. No fluid loss at all that I can find, reservoir is full to the top. No leaks at any of the calipers or wheel cyls or lines. Everythings new but booster and master.

Using the haynes and toy FSM I come up with the following after using the test procedures for the booster they outline:
Q. Engine stopped and press pedal several times, pedal travel shouldnt change.
A. pedal travel becomes less.

Q.Brake pedal fully depressed start engine, pedal should sink a little when engine starts
A. Pedal sinks at least a good inch or better

Q. Depress brake pedal, stop engine and hold.
A. Pedal doesnt seem to sink I think, its hard to tell b/c it sinks a little if any.

Q. Start engine, let run for a min. Turn off and then press brake pedal several times. Pedal travel will decrease
A. Pedal travel does decrease.

I also rechecked the pushrod, yep its adjusted where I had it last I measure. I did notice theres quite a bit of in and out play at the rod-is that normal? Also noticed if I grip the rod with pliers (so I can adjust it) it hisses if I dont keep the pliers straight.

No leaks anywhere, not even at the master seal. I just adjusted the pushrod again maybe 1/8" at most and bingo firm pedal again. Maybe the springs or whatevers inside the masters wore out? At this point its either replace one or the other-master being much cheaper first.

IDK...

[Seanz0rz]

I wish I could help so bad! I have never had to deal much with the brakes, so I don't even know where to start.

[CJM]

I hear ya Sean.

It seems the truck is cursed, I fix one thing and a new problem crops up. I paid alot of coin to get the frontend done and a steeringbox and it still aint right-but I can deal with that vs not being able to stop properly.

I googled around and found that someone mentioned the master could be leaking internally in itself with no evidence of fluid leaks. $70 for a new one I might as well do it sooner or later I guess. Booster is $250 from rock auto!

For sure should I save up some coin Im gonna buy a super duty, 200-300k on many Ive seen and I aint ever seen issues like I got even if the ford wasnt cared for all to well. Plus parts are cheaper! Toyota wants way to much for thier stuff still and resale is still very high.

[corax]

I wish I could help so bad!


Ditto, but with all you've done I wouldn't know what to suggest without physically being there and seeing the truck.

I know you said the front end was recently re-built. This probably isn't your issue either, but I used to get an intermittently low pedal that I could pump up and then would be normal again for days/weeks/hours. It usually happened after extended driving through through the twisties at speed (SoCal desert at the time). The cause was "brake pad knock-back" Again, probably not what what you're dealing with, but more reading on it here: http://stoptech.com/technical-support/technical-white-papers/pad-knockback

[CJM]

Interesting info Keith, but I doubt its my issue.