Brakes sticking

[keiichi]

Car - RT142 Corona

motor - 22RE

use - Drifting

problem - After driving for a bit the brakes stick on harder until it is undrivable and you must pull over. See below for full details.

occurs/started when - The car had been sitting around unused for about a week in this very rainy and humid weather we have been having then took it for a hard skid and started shortly after that on the way home.

personal situation (if applicable) - I don't get the joke.


Ok.... so I have troubleshooted it a bit. Brake system has been completely flushed, about 1 liter has been put through, and it still occurs so not the fluid.

When the brakes get hot from the pressure build up ALL get hot, so it isn't an individual caliper.

The fluid in the master doesn't get hot if that is relevant. Which is also a fairly new master (like a couple years or so).

There are no leaks.

I have tried sitting stationary and pumping the brake for about ten minutes and it does not occur, you can roll the car easily by hand, has to be driven i.e. warm the brakes up.

Now here's the weird part (or atleast weird to me), if you pull the vacuum hose off the booster it releases the pressure, making a big whoosh noise and freeing the calipers making it smooth rolling again. Remember, it only occurs if the car has been driven not with the car running and the brakes pumped stationary.

This doesn't seem to make sense.... any ideas? Please? :P

[keiichi]

hmmm i should mention, just realised now, that i didnt test if it built up pressure stationary while revving it, will have to check tomorrow.

[R&D Mechanical]

lubed caliper slides?

[keiichi]

thanks but can't be that, as releasing the pressure from the booster resets the brakes to optimum operating condition again... also, the front and rear brakes are of a different age as i converted to silvia front recently and the brakes failed at the same time and in an even manner.

[Cerby86]

one way valve in the line to the booster round the wrong way?

[keiichi]

if someone broke into my car popped the hood and inverted it in the two or so weeks it was sitting around then maybe :P but it was working fine before.

[lolwat]

could so be slides, if it pushes the brake then the slide are jamming up only one pad will release pressure and the other will still be stuck up against rotors

[Cerby86]

yeah I sort of doubted it would be the problem but I figured you shouldn't leave any stone unturned lol
Surely if the pressure is building up in the booster and letting that off fixes the problem then it has to be at the booster end?
That pretty much leaves swapping out the booster to see what happens. Which is totally gay.
Never tried it myself but maybe some high pressure air blown through the booster? Or even a little squirt of wd40 (probably really bad lol )

[keiichi]

yeh - the thing that confuses me is the booster getting stuck only when heat gets in the calipers - as i said, pumping the brakes stationary doesnt do anything, so heat getting in the slides making them stick? will check the slides, maybe one half is getting stuck on and releasing the booster pressure sorts out half the problem :S doesnt really make sense tbh lol

maybe its just the revving the of the engine that makes the booster stick or something not the actual use of the brakes, will check that tomorrow also.

dont think putting wd40 in there would be bad, something is sticking, so couldnt hurt tbh - atleast in the sense that if it is already stuffed anyway and they arent rebuildable.

[keiichi]

ok so found out its nothing to do with the calipers, tried just revving the engine and pumping the brakes and that gets them stuck on, revving the engine alone doesnt get it stuck on. releasing the pipe from engine side of the check valve doesnt relieve the problem, turning the engine off and pumping the brakes also relieves the problem.
whaaa?

[KENut]

Sounds like a booster problem man.

Actually, so initially you removed the pipe from the booster side? And that released pressure.

But not when you pulled off the pipe on engine side. You checked which way the valves pointing yeah?

[keiichi]

yeh the valve can only go one way, and it is definitely on the right way. anyway, booster problem, seems a bit odd for it to fail from sitting around but replace seems eminent.

[keiichi]

....and it has been replaced....

by another problem that is, original problem fixed but now it is like it is over boosting with the new booster (off a 22re corona too). you can practically push the pedal to the floor with your breath and it feels like there is no feedback but about halfway through the travel the brakes will suddenly engage (over about the travel of an inch or two), which is about normal but seems sudden due to no feel.

any ideas!? I'm totally stuck here, been asking around, fiddling around and researching on the net all day. nobody has any idea - according to the trouble-shooting guides i have followed the booster is fine.