Originally Posted by 71mitch
I have a 49 Olds with an after market under the car 7in booster. It was on the car when I bought it so not positive of maker but the master cylinder looks like 68-72 corvette. I lose my brakes at an idle and the pedal gets real hard. When your moving down the road the brakes are fine. Would this indicate a bad booster?
Does the pedal "sink" when at idle? In other words, do you push on the pedal and after a while it slowly goes down, and at that point you lose your brakes? This could be happening without you noticing so if you don't know for SURE, get out there and try it.
Just apply pressure and note the pedal height....keep the pressure there.....and see if the pedal sinks.
If this is the case, it's the master cyl that is leaking internally.