SSBC power front disc vacuum booster and MC issue
My new to me 1966 Mustang 2+2 has been modified to a SSBC power front disc brake kit and OEM drum rears. The brake pedal goes nearly to the floor if you pump the brake with the engine off and the vacuum bleeds off as you pump.
The problem is the pedal doesn't automatically return to a full height pedal once you start the car. I have 18 psi vacuum at idle so the booster is getting plenty of vacuum. I tested the vacuum booster by pulling the vacuum check valve out and found the booster still had vacuum in it after 3 hours with the engine off so it shouldn't be leaking.
If I reach down and pull the pedal up with the engine running, it returns with a small pop to a full pedal and the brakes function normally again. So someone help me explain what is happening. It's as if the booster diaphragm bottoms out once the vacuum is gone and doesn't return to normal until you pull the pedal up. I'm assuming the problem is just in the booster and not the MC. What's wrong and what would you replace? Thanks.
1966 Mustang 2+2, A code, AOD AT, PS, PDB, AC, Pony deluxe interior
Last edited by poqman; 12-17-2017 at 08:00 PM.