power brakes

[mister mike]

Have looked on FAQ and no help yet. Replaced std brake mc and went to a power booster with a new mc, and at the same time added rear disc. Install went well and bled the brakes first with a vacuum bleed system and then went to all four corners and got great pedal. Started truck and have no pedal at all. No brakes goes right to the floor. Shut truck off, two quick pumps and solid pedal again. I do get red brake light on at bottom of pedal stroke with engine running. What am I missing here.