Folks,

Would the Brake Master Cylinder be responsible for the following
symptoms:  Pedal is hard and there is no pumping needed to stop but if
pedal remains depressed,  eg such as waiting at a stop light, and
allowed to move up and down slightly, it will slowly sink to the floor
over the course of several slight up and down pumps. I have re-done the
back brakes: drums,  shoes, cylinders,  and they are adjusted and bled.
I also see no fluid leaks fore or aft.

Someone earlier suggested, as a check on the brake booster, to press the
pedal and hold and start the engine and confirm that the pedal sinks a
bit as a confirmation that the booster is working properly. I have done
this and it behaves accordingly.

It seems pretty evident that the MC is starting to pass pressure, but
thought I would confirm before I replace another part.

-john