Soft Brake troubleshooting

[Styleprojekt]

So what happens is that when I push on the brake pedal, i get the expected increased resistance until all of a sudden (about 3/5ths of travel) the resistance is completely gone and the just pedal feels dead...pushes all the way through with ease.
I bench bled my master cylinder and it feels fine (as far as I can tell ). I noticed that the brake booster lets a LOT of air escape when reaching the no resistance point. It all escapes through the airhose that recirculates into the intake.

Is this a sign of a bad brake booster?

[jlevie]

That is not a sign of a bad booster, but rather a sign of a bad master cylinder. The seals in the master cylinder are failing and when you achieve sufficient pressure the seals open and release pressure, which causes the pedal to go to the floor.

[5Toes]

Not to thread jack, but my car, when I push down on the brake pedal while stopped, there is a vibration. Sort of strong, but not oo bad. This is only when I am stopped, while braking down from a given speed, the pedal feels great.

Any ideas?

[jlevie]

Not to thread jack, but my car, when I push down on the brake pedal while stopped, there is a vibration. Sort of strong, but not oo bad. This is only when I am stopped, while braking down from a given speed, the pedal feels great

I think that would have to be the ABS or a bad booster. Have someone hold pressure on the brake pedal while you place your hand on the ABS unit. If it is the cause you should be able to feel vibration.

[5Toes]

I sure hope it is not the booster! Eek!