Even w/new brakes all around, professionally installed and re-bled, I have low brake pedal complaints. This is a high-mile G20 series Chevrolet Sportvan w/ABS. Is there a test for a faulty power brake vacuum booster for these trucks? Any help appreciated. WJ

 

It might not be the booster, but the master cylinder instead. I don't know about testing a booster, though. I guess you could check to make sure the engine is pulling enough vacuum.

 

I know the vacuum's fine...At this point, think I'll just have both master cylinder and vacuum booster changed....Appreciate the help, snakeoiler. Anyone else contribute to this? Thanks. Also: What is the test for determining whether or not the master cylinder needs to be changed? WJ

 

what year van is this?
the booster shouldnt cause a low pedal, the only way to test i think is to put vacum to it and check to see if it leaks (with a vacuum pump)
to test the master cylinder,plug both ports with pipe plugs, effectively ruling out everything below the master cyl.the pedal should stay hard if its good.
on most newer GMs if the abs motor and valves get empty of fluid(during service, a leak or whatever reason) a dealer needs to do some procedure to run the system to get air out of it,it cant be bled out even with a pressure bleeder good luck