Brake Problem - Help!!!!!
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Joined: Oct 2000
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Brake Problem - Help!!!!!
I bleed brakes twice on my 74, drove for a few days with a very hard peddle and peddle went to floor on cold start. I checked MC and I was low in rear and high in front reservior. Could air in the system cause this and under what circumstances would brake fluid exchange from front to back? I do not think that 74 and earlier had a real proportioning valve that would exchange fluid and think under certain conditions the MC could exchange fluid? I do not have a leak either! What's up here and should I go back to bleeding. Thanks.
John
John
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Re: Brake Problem - Help!!!!! (johnb74)
Sounds like it may be a master cylinder problem. It must be leaking from the back into the front through the plunger.
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Re: Brake Problem - Help!!!!! (johnb74)
John
I don't how fluid could transfer from back to forward reservior. If the master cly is bad, maybe (but that is a big maybe), but you should see this in the peddel going to the floor. Now lets assume the calipers are good, thats leaves the master cly sucking air into the rear break system. I would re-bleed the system, make sure the peddle is not bleeding down, and monitor it. The only other ave is to start throwing parts at it. $$$$
I don't how fluid could transfer from back to forward reservior. If the master cly is bad, maybe (but that is a big maybe), but you should see this in the peddel going to the floor. Now lets assume the calipers are good, thats leaves the master cly sucking air into the rear break system. I would re-bleed the system, make sure the peddle is not bleeding down, and monitor it. The only other ave is to start throwing parts at it. $$$$
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Re: Brake Problem - Help!!!!! (johnb74)
My guess would be a leak. It could leak out of the master cylinder into the booster, but it's supposed to leak out between the booster and the cylinder when those seals fail. It most certainly has to be a leak though, where else could the fluid go? Was the front compartment overfilled or just much higher then the rear compartment?
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Re: Brake Problem - Help!!!!! (johnb74)
I have a 75 and had the EXACT SAME problem a couple of weeks ago. Took my Vette to the local Chevy/Corvette dealer and they diagnosed the problem to be the master cylinder. The dealership said the master cylinder was "by-passing"...what ever that meant.. All I wanted to do was get it fixed. After they replaced the master cylinder & bled the brakes, they worked PERFECTLY. :thumbs:
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Re: Brake Problem - Help!!!!! - See my last post
Thanks guys! I need to re-check whether I have a leak in any caliper. Does anyone know under what conditions the MC by-passes between reserviors. I would assume worn o-ring seals on double cylinders? I also did not mention that this all started when I changed the front brake pads and sucked in air when I un-froze a stuck caliper piston. The MC worked fine before. I may well be sucking in air on that caliper and probably need to pull it off and check. I do not see a leak with the wheel off, but it may be small? What do you guys think?
John
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Re: Brake Problem - See Last Post (johnb74)
John, I'm not trying to be "smart" but I asked a question in my post (3 spaces up) that was not answered, so it's difficult at best to give any additional feedback. Hopefully someone else might have an answer, but I guess I would continue looking for a leak if you are loosing fluid from the rear chamber.
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Re: Brake Problem - See Last Post (Big Fish)
If you got no leaks and everything appears properly together, then bleed the **** out of them and see what happens. It might take you a quart+ of fluid to get it but you might just get lucky.
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