brakes not relieving pressure??

[rapedbytheeves]

so ive had problems with the brakes ever since i got my 1990 eagle talon tsi awd 3 weeks ago, blew a line so i replaced it and bled the brakes all the way around. they seemed like they didnt have enough fluid in them at first since you could push the brakes all the way down pretty much before they would engage. but now, they act normal for about 10 minutes and then get stiffer and stiffer, tell there is no play at all in the brakes. Then start sticking to the calipers and get super hard to push down. i eventually have to pull over, crack one of the brake lines on the proportioning valve, after that they work for about a half hour then start to do it again. the whole process repeats istelf. i also noticed before i started cracking the lines every now and then that my brake reservoir would be low after i filled it up the previous day. seems like it gets worse when i add the fluid to get past the low mark. idk where its going i dont have any leaks i dont think. theres never any fluid on the ground. i know its not a sticking caliper because the caliper would stick after i cracked the line open. they do not. it seems like the pressure just keeps building up and up and up until the brakes stick on. anyone got any ideas?

anyone?

 

[EuroDriver]

I think it's your master cylinder. If there are no leaks anywhere else and the lines are good. It's gotta be the source. It leaks inside at the seal between the booster and --> brake pedal. The leaks are hard to see.

 

[rapedbytheeves]

yea i heard brake boosters rarely go out and you can hear hissing from them. i cant hear any hissing and i was kinda leading to that too ill replace that and see what happens thanks man if anyone else has any feedback feel free to leave some. also how so i get all that brake fluid out of the booster?

 

[EuroDriver]

BRAKE BOOSTER OPERATING lNSPECTION

For simple checking of brake booster operation, carry out the
following tests.

(1) Run the engine for one or two minutes, and then stop it.

(2) Step on the brake pedal several times with normal pressure. If the pedal depressed fully the first time. but gradually becomes higher when depressed succeeding times, the booster is operating properly. If the pedal height remains unchanged, the booster is faulty.

(3) With the engine stopped, step on the brake pedal several times with the same pressure to make sure that the pedal height will not change.
Then step on the brake pedal and start the engine. If the pedal moves downward slightly, the booster is in good condition. If there is no change, the booster is faulty.

(4) With the engine running, step on the brake pedal and then
stop the engine. Hold the pedal depressed for 30 seconds. If the pedal height does not change, the booster is in good condition. If the pedal rises, the booster is faulty. If the above three tests are okay, the booster performance can be determined as good.

If one of the above three tests is not okay at last, the check
valve, vacuum hose, or booster will be faulty.

 

[rapedbytheeves]

its like the bottom right picture but all the time, when engine is started and stopped. then they get so tight that the brakes lock up pretty much and the car wont move

the first two tests checked out good, the last one i couldnt really tell a difference. the pedal didnt change until i let off of it and stepped back on it and then felt stiffer.

 

[EuroDriver]

Well.. the master is left.

 

[rapedbytheeves]

i looked up some stuff on how to test that and the only signs i could find were sinking brake pedal which it did before the stiff pedal only thing happened and im really lookin at that as being the problem but ive also heard that the proportioning valve could be the problem... although ive heard mixed opinions, i really wanna fix my car and also resolve this topic to this site for future reference to help others that might get this same problem.

 

[92AWDTalonTSI]

Is it all four wheels? If not pull a caliper and you should be able to push the piston in with moderate force. If you can't do that. Looking into your soft lines. I had the very same problem on mine. The would allow pressure by but not back. I replaced them and now it stops fine.

 

[rapedbytheeves]

mostly the front two and right rear, some reason the left rear isnt very hot but the others are. thats really weird that the soft lines would cause that problem, do they get old and gunked up or what? and why would cracking the line help relieve them? its mostly the right front that sticks but now the left front and right rear are doing it so im kinda ruling out the caliper is faulty since it releases from the rotor when i crack the brake line at the proportioning valve. if i had the money id just replace the whole entire brake system and be done with it!! haha

 

[90moneypit]

Well a bad soft line usually gives you a soft pedal due to expansion. Are you sure you bled all the lines correctly last time? A set of speed bleeders goes a looong way towards fixing the 'did I do it right?' question. Brake fluid is pretty cheap unless you're going full race synthetic dime stopper never boil with bling additive. So I'd try bleeding them one more time. Then again, if you don't know when the last time the lines were changed it wouldn't hurt to look. They may still be the factory lines getting ready to turn 21 years old. Braided are expensive but if you look around online you can get rubber ones for cheap.

 

[rapedbytheeves]

ill try bleeding them again but why would they get stiffer and stiffer as im driving? even if i dont touch the brakes they get stiffer and stiffer until they start to lock up on the calipers

 

[ramsack]

sounds like you have water in the brake fluid. do a full flush of all the fluid before you ruin your calipers.

 

[housegsx]

Are your flex lines still in good shape or are they originals? If they are expanding alot under braking the hose could be trying to contract back to it's original diameter after you let off the brake pedal. This could possibly cause the line to create pressure in the system.

Both of my rear calipers were hanging up causing a ton of wear and heat. I had to replace the proportioning valve to fix it. It might be something to check, but since it's your front brakes we are talking about I doubt that is your issue since the proportioning valve doesn't limit pressure to the front calipers, only the rear.

Also, from all the cracking open the lines and excessive heat build up in the calipers you most likely have a ton of air in the system. Re-bleed all 4.


Edit: You only replaced one line that blew? Was it a front line? If so, at least replace the pair so both fronts are new, but might as well do all 4.

 

[delta448]

Something is blocking the brake fluid from returning, and since cracking a line open on the proportioning valve solves the issue, the problem is somewhere between the proportioning valve and the master cylinder.

When you step on the pedal there's several hundred psi of pressure forcing brake fluid through the lines easily passing through a minor restriction, but when you let off the pedal, the only thing that pushes fluid back into the resevoir is the pressure difference you created when you depressed the pedal. If something were to either constrict or occlude a single brake line, the corresponding caliper would slowly build pressure until it could not return enough fluid to release at all. Since you have multiple calipers sticking and since cracking off the pressure at the proportioning valve solves the issue, we know that the problem is somewhere north of the proportioning valve, or in the valve itself, which is my hypothesis.

 

[ramsack]

moisture...

my mr2 did the same thing. i wouldn't even have to use the brakes and they would lock up on their own. flushed the system and the problem went away.

 

[delta448]

moisture...

my mr2 did the same thing. i wouldn't even have to use the brakes and they would lock up on their own. flushed the system and the problem went away.

Flushing the system will solve the vast majority of all brake system issues. I wouldn't be so sure that moisture is the problem with his just because flushing yours fixed it, even though moisture was the most probable cause in your case.

 

[rapedbytheeves]

thanks guys those are all very good possibilities. im gonna bleed the whole system again and flush it, since that would be the cheapest thing to do right now, i only replaced one line going to the rear from the proportioning valve, the left rear to be exact. all my soft lines look to be in good shape, they are not cracked or faded really, dont look weathered either i tried squeezing them and checked all of them for bubbling and soft spots and they all seemed good. how do you flush brakes im sure i can search and find something on the web but do you just keep running new fluid in it over and over like a bottle or two through the system? thanks so much guys i really really appreciate it!!

 

[ramsack]

it's just like bleeding them with a big vac pump. you just keep sucking fluid through the bleeders until you see new stuff coming out and keep the reservoir full. start left rear, right rear, front right, front left. longest line first, shortest last. no need to "bleed" since this is the same thing really.

i also don't see how a soft brake line going bad would cause this. brake systems run 1000-2000 psi. if something is going to malfunction in a rubber hose at those pressures, it's going to pop, not implode.

 

[rapedbytheeves]

so how do i suck the fluid out i need a pump?

 

[92AWDTalonTSI]

Yup, you can use a pump from Harbor Freight.

You must be logged in to view this image or video.

I think you can rent the at Autozone too.

 

[ramsack]

your hand will get tired using one of those pumps. the canister that comes with them are also tiny. a bigger canister and a crapload of vac hose and you can just use your car's manifold vacuum to do the job quick.

 

[rapedbytheeves]

wouldnt i just be sucking that into my motor then?

 

[90moneypit]

your hand will get tired using one of those pumps. the canister that comes with them are also tiny. a bigger canister and a crapload of vac hose and you can just use your car's manifold vacuum to do the job quick.

wouldnt i just be sucking that into my motor then?

Look at the picture above his post. See that white plastic container with two connectors on the top lid pointing in opposite directions? He means a larger one of those so you don't suck fluid into your engine. It acts like an oil catch can in a way, fluid goes in and air goes out. I've never used that technique but it's the same principal as using the hand pump, just replacing the hand pump with an engine.

 

[ramsack]

with the engine as a vac source it's a constant ~20 inHg of vacuum wheres you will never hit that bleeding brakes with a hand pump. a good idea is also to have the container above the level of the maser cylinder with little vac line as possible running from the caliper to the canister so air doesn't just float back up into the caliper.

 

[EuroDriver]

Let us know how this turns out..