Hey everybody. Say I have maybe a dumb question the other day while driving my 92 Z28 5.7 TPI i was at a stop light and when I let off the brake to move up a little bit and reapplied the brake the idle when up a little and i was wondering could a bad brake booster cause that . I know the brake booster works off vacuum from the motor so could something in the booster be causing a vacuum leak from time to time. Please forgive me if this is a dumb question.

 

Feels like the pedal pumps up a little when stepping on and off? I wouldn't aim at the booster, I'd aim at the master. Or possible air.

 

Thanks for the reply aliceemprie. And i do have a new master cylinder i bought some time ago so I'm going to go ahead and track down a brake booster as well I know this car set up for some time before i got it and it wouldn't hurt to go ahead and replace them at the same time. The brakes do work but at times it dose feel like it dose give a little sometimes.

 

A bad brake booster would act like a vacuum leak and increased pedal effort.
A bad master cylinder could "give a little sometimes" if brake fluid leaks past the master cylinder. Usually a master cylinder fails more consistently with no pedal pressure or stopping.

"when I let off the brake to move up a little bit and reapplied the brake the idle when up a little" Depending on the amount of time for this operation, vacuum hadn't been built up completely in the booster, when the control valve opened again when the brakes were re-applied an amount of air where there would normally be vaccum re-entered the intake.

This could be a problem in the booster control circuitry or if there is an independent check valve.