Hey guys, I need to consult the brain trust on what I think is a booster problem.

73 Barracuda Power disk/drum, adj prop valve.

I have been completely through the brake system, new rotors, drums, shoes, pads, rebuilt calipers, new style wheel cylinders with residual valves, 1 1/32 AL MC listed for a Gran Fury, parts store reman booster, PR clearance set at .020" using a tool.

The hydraulics are fine, properly bled and functioning.

So, my factory brake booster died, but before it did, the pedal got very soft and would travel about half way before any meaningful braking started, and then I let off the pedal and I have immediate braking when pushing the pedal. Then the booster failed completely.

Parts store reman booster, same pedal behavior. I don't doubt that my rebuilt booster could be a POS, but my inner A&P loathes throwing parts as a troubleshooting measure.

I have tested the booster using the FSM method and methods I found on the interwebs. It seems to pass those tests, but I dunno.

Can anyone put a finger on what would cause these symptoms? I am befuddled. Faulty booster is where I'm at...

Thanks