Hrm I am having odd brake problems. I suffered brake failure, so tried first to bleed the system. It never bled right, as I could not 'pump up the pedal'. I did a little asking around and was told the seals in the master cylinder could be blown, so ok, replaced trhe master cylinder. I bled the system again, and to my surprise, could pump up the pedal! Now the strange problem.... When I start the car, when I intially hit the brakes, nothing. I take my foot off, and the pedal SLOWLY returns to up postion. I press again, and they give a bit of braking, I repeat again to be able to stop. In effect, I have to pump the brake to get pressure enough to stop. This is not good. The system was bled right, no hoses are leaking, no pipes are crimped, the light doesn't come on, adaquate vacuum to booster, and brakepads and cylinders seem fine. I have been told several things to try, but would like to ask the community.
'85 Camaro IROC [LB9] : 4 wheel disc brakes
brand new master cylinder
Only lost 1/2 gallon of brake fluid bleeding and re-bleeding the ___ brakes.

Any help is most appreciated.

 

sounds to me like the brake booster is toasted.

 

Sounds to me like the master cylinder needs a "bench bleed"... you did do that before you put it on of course? If not, the line fittings on the MC aren't the highest point in the chambers of the MC; and because of the slant that it sits at, the remaining air will never come out while it's in its normal installed position. You'll always have some trapped in the MC (alot actually).

 

the seals in the master cylinder could be blown, so ok, replaced trhe master cylinder. I bled the system again, and to my surprise, could pump up the pedal! Now the strange problem.... When I to stop. This is not good. The system was bled right, no hoses are leaking, no pipes are crimped, the light doesn't come on, adaquate vacuum to booster, and brakepads and cylinders seem fine. I have been told several things to try, but would like to ask the community.
'85 Camaro IROC [LB9] : 4 wheel disc brakes
brand new master cylinder
Only lost 1/2 gallon of brake fluid bleeding and re-bleeding the ___ brakes.

Any help is most appreciated. [/B][/QUOTE]

Since you've already replaced those things, i would also suspect the brake booster leaking. However, the proportioning valve can cause strange brake problems when it fails. I've had to replace one before, with similar problems.


When all else fails, bleed the master cylinder again. I know you've already done so (a lot) but anyone who's replaced one can tell you how frustrating they can be sometimes.

Good luck!

 

since ii'm getting so used to it, it shouldn't take me too long to re-bleed the master cylinder (done 3 times, once on the old one, twice the new)... i doubt there is any air left in it... i used a vise, etc... like the dircections said to. i still don't have the idiot light popping on (yes, bulb is ok) and when i test out the booster, the light does come on when it's supposed to (which should mean the light is ok, as well as the booster) i'm starting to suspect a collapsed hose... what do you all think?

 

On my car I had the same problem, my brake lines got extremely old and worn, and the rubber hoses began to have weak spots where the pressure made it baloon out VERY much. After replacing all my lines with braided SS, the problem stopped. If you wanna check out your lines for either worn spots or lighter spots, the parts that ballooned on mine were a lighter color than all the other hose. Good luck!

 

With checking hoses, have a bud press the pedal down and you look for swelling under the car at the hoses. All in all, you may just want to replace all of them as they wear over time and pit and allow moisture into the brake fluid. And water compresses, which is bad.

 

I thought water doesn't compress... (which is why you don't want water to get into the cylinders... it can start breaking rods because it won't compress.)