MG Car Repair: Brake problem, brake failure, rear cylinders

Question
The brakes on my '80 B were half shot.  I replaced the rear cylinders, one of the pipes, and the rotors.  Now they work OK except that the pedal sinks gradually to the floor while I'm at a red light.  Does this always indicate an interior leak or can it be caused by improper bleeding?

Answer
Hi Billy.  Sounds like the master cylinder main cup is worn or partially collapsed, allowing fluid to leak past when the brakes are applied.  Improper bleeding would show up as a spongy pedal, a completely different symptom, because the pedal bounces rather than slowly sinking.

You must fix it as soon as possible, because it could get worse at any time and result in total brake failure.  If that happens, remember that pumping the pedal (lifting off the brake pedal and re-applying) could save your life.