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Discussion Starter · #1 ·
So in my last thread, the clutch and the brakes were sloppy. Now after blowing the clutch master cylinder (while bleeding the clutch line :bigthumb: ) and finding out the brake master cylinder was leaking, I replaced both of them and bled the systems. The clutch now feels good and is functioning properly, however the brakes are still crap. They pump up and get tight, but then if you let them sit for like 10 seconds they get squishy and lose all pressure again? What the hell is going on with this car? Longest brake job in history :(

Any suggestions or ideas? Thanks again, Drew
 

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So if you hit the brakes like 10 times in a row quickly, they get tougher and tougher ? And if you hold it down the last time it eventually softens up ?

This is normal, the first 5-7 times hitting the brakes will be normal and it will get tougher from then on. This is because a brake booster can only boost for a few times in a row, as you are actually using a certain amount of build up pressure when you hit the brakes. Then if you hit it again you lose another certain amount of pressure and so on and so on.

So at a certain point, the pressure is gone and the brakes get tougher as your foot needs to compensate the lack of pressure by pushing harder. But a brake booster is working all the time and starts building up pressure again when the pressure leftover is too low. That's what you feel when you keep the pedal pressed, the booster is building up pressure and therefore your foot has less pressure to compensate.

That's why the brakes tend to feel squishy after holding it down a bit after hitting it a few times.
 
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Discussion Starter · #3 ·
C44 said:
So if you hit the brakes like 10 times in a row quickly, they get tougher and tougher ? And if you hold it down the last time it eventually softens up ?

This is normal, the first 5-7 times hitting the brakes will be normal and it will get tougher from then on. This is because a brake booster can only boost for a few times in a row, as you are actually using a certain amount of build up pressure when you hit the brakes. Then if you hit it again you lose another certain amount of pressure and so on and so on.

So at a certain point, the pressure is gone and the brakes get tougher as your foot needs to compensate the lack of pressure by pushing harder. But a brake booster is working all the time and starts building up pressure again when the pressure leftover is too low. That's what you feel when you keep the pedal pressed, the booster is building up pressure and therefore your foot has less pressure to compensate.

That's why the brakes tend to feel squishy after holding it down a bit after hitting it a few times.
Well it does do like you said, looses pressure while holding the pedal down, but it also does it while not holding the pedal down. So if I were to pump the brakes until they get tight, like 3-5 pumps, then release the pedal and not touch it for 10-15 seconds I loose all that pressure and I have to re-build up pressure again, by pumping the brakes. Is it possible the booster is leaking?
 

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nah that's normal, i don't know what brakefluid you use, but why not use a higher density one ?

Even when you pres it 5 times half the pressure is gone and feels really tough. That's when the booster is working already to build pressure again and that's why it feels soft next time again.

If you feel it is too soft for your liking, use steel braided brake lines instead of the standard rubber hoses and use a brake fluid with a higher density.
 
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Discussion Starter · #5 ·
C44 said:
nah that's normal, i don't know what brakefluid you use, but why not use a higher density one ?

Even when you pres it 5 times half the pressure is gone and feels really tough. That's when the booster is working already to build pressure again and that's why it feels soft next time again.

If you feel it is too soft for your liking, use steel braided brake lines instead of the standard rubber hoses and use a brake fluid with a higher density.
I see what your saying, but the softness of the pedal when it loses pressure is not a little. Its alot (sorry I should have stated this before) like I would jam the pedal to the floor and the brakes would barly apply. So instead of coming to a sudden stop, I would go to a rolling stop (at 40mph + jam on the brakes = complete stop after 40 feet or so) I have Steal braided brake lines already (ebay specials) and Im using Dot 3 brake fluid.
 

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Are you losing fluid somewhere ? Perhaps near the abs unit or in the calipers ? Bad junctions ?

Maybe you should check the abs computer for codes (look that up in the tsrm), maybe that will throw an error.

And if all else fails... try thicker brake oil. I use a DOT6.1 ;)
 
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Discussion Starter · #7 ·
C44 said:
Are you losing fluid somewhere ? Perhaps near the abs unit or in the calipers ? Bad junctions ?

Maybe you should check the abs computer for codes (look that up in the tsrm), maybe that will throw an error.

And if all else fails... try thicker brake oil. I use a DOT6.1 ;)
ok, will do. Thanks for your help
 
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Discussion Starter · #8 ·
I seem like I have the same problem. For instance, if a stop at a red light for example in a hill, I cannot keep the pressure in the brakes. The pedal will slowly move to the floor. But if I just release the pedal and put pressure on it again, it will work nicely.
 

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It could also mean your MBC is leaking... if you have the opppurtunity to replace it, i would say try that. I have no idea if one could repair these things themselves, i think not.
 
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Discussion Starter · #10 ·
I got mine rebuilt from autozone for $40 with core exchange. You can rebuild them your self, but I couldn't find any rebuild kits for it.
 
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