I'm not sure if this applies to your bleeding problem, but I recently replaced a master cylinder and had a problem bleeding and getting good pedal pressure. Turned out that I just needed to adjust the rod, that presses the master cylinder piston (attached to the brake pedal). It was turned in so far that the pedal was almost to the floor before it even contacted the master cylinder piston. I turned it out so the pedal only had to be depressed about 1/4" inch before it started to press the MC piston. Then I rebled all four wheels and had a full pedal with great breaks.