91 Chevy cavalier

Did the problem exist before you did all the brake work?

, brake pedal is good. When engine is on, pedal goes to the floor. Have r eplaced shoes, rotors, calipers, and 2 masters cylinder (one rebuilt, one n ew. The brake pedal makes a hissing, when pushing the brake. Sounds sort o f like air in a vacuum line. i'm thinking the booster needs replaced, any thoughts or suggestion?

the noise has always been there; but sometimes the brake worked and sometim es they didn't.

brake pedal is good. When engine is on, pedal goes to the floor. Have rep laced shoes, rotors, calipers, and 2 masters cylinder (one rebuilt, one new . The brake pedal makes a hissing, when pushing the brake. Sounds sort of like air in a vacuum line. i'm thinking the booster needs replaced, any t houghts or suggestion?

You have air in the system. Bleed the master cylinder and then the lines.

Worked? Do mean sometimes the pedal went to the floor for years now? OR, has it only been since the m/c has been changed? The noise is normal for the amount of time that the pedal is moving. Once the pedal stops there should be no hissing.

brake pedal is good. When engine is on, pedal goes to the floor. Have rep laced shoes, rotors, calipers, and 2 masters cylinder (one rebuilt, one new . The brake pedal makes a hissing, when pushing the brake. Sounds sort of like air in a vacuum line. i'm thinking the booster needs replaced, any t houghts or suggestion?

vacuum line.

problem has existed off and on for a couple of years. It worked after the first m/c was changed. Then a few days ago, it went to the floor again. When we checked it , didn't seem to be working consistently on all 4 lines when depressed. So new one was put on. We bled and bled with both engine o n and off. lt stays up till engine is started. Then it goes clear to the floor.

pamela efaw wrote in news: snipped-for-privacy@googlegroups.com:

it is not the booster, it cant do that. when you replaced the rear brake shoes did you adj them up properly? KB

If you properly bled the master cylinder and lines and you're not losing any fluid, I would open up the rear drums to make sure they are working properly. If the rear brakes check out OK, then your master cylinder should be replaced again.

ok. Do the brakes stop the car from moving when the pedal goes to the floor? I am leaning towards a bad m/c.

Air is getting into the system somewhere. From the description of the hissing sound, it's likely at the master cylinder, but it might be at a damaged brake line or fitting on the master cylinder.

--scott

I half way remember a couple of jobs that had bad air valves in the boosters. The pedal would go down and lock the brakes. Another one had a m/c replaced and the push rod was the wrong length and the same thing happened - push lightly on the pedal and it would lock the brakes.

The important part is whether the brakes lock when the pedal goes down. If so, it's the brake booster. My guess is that it does. Good catch. Looks like it's Miller time. :)