1995 grand am

[kbfunbeach]

brake pedal hisses under the dash board when i press does not stop til i let up what is the solution im all ears sometimes it goes all the way down and then gets hard to press

[doctorhrdware]

Sounds like it might be a master cylinder problem, or you may have air in the brake lines.

[mo_86_05]

mine had made a similar sound when i first got mine and when i had my brakes changed, i had the mechanic to look at it and there was something on the line that needed to be greased. Doesnt help out a whole lot since i dont remember what it was, but you might could figure it out from here.

[automps]

Originally Posted by kbfunbeach

brake pedal hisses under the dash board when i press does not stop til i let up what is the solution im all ears sometimes it goes all the way down and then gets hard to press

Brake booster is bad ! The Seal at the back is leaking . At the rod to the brake pedal

[3100]

automps is right, the vacuum diaphragm inside of your brake booster (big black round thing on the driver's side) is leaking.
- it is definitely bad, but if you want to test is do this. pump the brake pedal with engine off until it gets hard and stays up, then start the engine while keeping pressure on the brake pedal it should go down completely. If not it is bad.

WARNING: it is very dangerous to continue driving your car like that

before you do anything check the vacuum line that goes to the booster and make sure it firmly attached to the booster and that there are no leaks around the grommet.