I installed a new brake booster and cylinder in my 72 convertible. Bleed the brakes and got a firm solid brake pedal. When the engine is running the brake has no smooth return when braking on and off. Stopping is great but the pedal feels weird. When I hit the brake approaching a stop it brakes well but the pedal sort of stays down if I lift. It does eventually push back out or under throttle but it doesnt feel right. Turn the motor off and its very firm. Any ideas?

 

Sounds like you still have air in the lines. Did you bench bleed the MC first? Is the booster pin correct for the MC actuator?

 

Who rebuilt the components?
Does the booster hold vacuum?

 

I bought the booster and master from Fucisks. They were for my model according to the website. The parts looked the same as what I took out.

f I still have air, I would get a solid firm pedal with no vacuum but under vacuum would get what I am experiencing?

 

You will have a solid pedal with no vacuum.