Brake booster going bad?

[Jaycenk]

Just replaced all of the brakes on my 98 tahoe. Replaced wheels cylinders and the front calipers are good. Had some blow by on the master cylinder so I replaced it as well. Changed all of the rubber hoses as well. I have bled the brakes so I have a rock hard pedle when the truck is off but it feels like I have a problem with the booster or something when it is running. I have a pedal that changes BIG time based on vac. When the rpms are up at say 1500 to 2000 and I jump off the gas and on the brakes I have a great feeling pedal. Nice and firm and little travel. When I let it idle while coasting and then hit the brakes it is a hell of a lot softer and travels further before having stopping power. Pumping at this point will do nothing. If I blurp the gas and jump back on the brakes I have a good pedal again and it stops on a dime. Is the booster bad or is there another culprit? I am having trouble figuring out where to start looking. Thanks for the help

 

[AtomicHoe094]

sounds like a booster. thats pretty much whats left.

 

[95slowhoe]

When my booster went bad in my hoe i had a super hard petal and the hard i pressed the pedal the more the brakes applied. I found it was bad by rolling up the windows, turning off the radio and blower motor. Then i pressed the brake pedal and heard a faint hissing sound and knew it was bad.

 

[sumo]

best way to confirm, get a vacuum or mighty vac with a gauge, If it dosent hold, you have a leaky master

 

[Jaycenk]

K thanks for the reply's I will try listening for the constant hiss and If I can't hear it I will put a vac gage on it and double check it.