89 Brake problem

[BgBlock69]

The other day I was driving and all of the sudden the brake light came on while I was braking, the pedal went almost to the floor and it took noticeably a longer distance to stop.

I notice and air like sound coming from the firewall area at the brake booster. So I thought that the problem was the booster, so I replaced the booster.

That did not correct the problem. Any ideas?

Also my back left brake sounded like that it would not release after applying the brake. It would make a rubbing noise when I take off from a stop. So I replaced the caliper, but that did not fix it, I still have the problem. Could I have mis-diagnosted that also?

 

[JT ZR-Won]

I'm not a brake expert but I wonder if it could be the master cylinder?

Jay

 

[Bob 89]

Sounds like the master cylinder to me, also.

Bob White

 

[Eagle85C4]

Off the back of the plenum is the connector for the booster on the drivers side. From the steel pipe it goes to rubber hose which connects to the front of the booster. Where it connects to the booster, the little piece the hose is connected to that makes a 90° turn into the booster is a check valve. It is quite possible the grommet is leaking or the check valve is leaking, both will cause the hissing sound. If you have already replaced the booster and it is proven good I would look at the hose and check valve. Let me know what you find....