ok scope this out, on my 91 crx si, i replaced all calipers, bled the brakes according to service manual, pedal sunk to the floor. it was fine before i replaced anything. but then again the caliper pistons were seized from sitting for too long and im pretty sure there was moisture in the lines. anywho, bought a new master cylinder hooked it all up, bled the brakes goes to the floor. pressure builds when the car is off but as soon as i turn it on the pedal sinks to the floor. the check valve is good and the only thing i can think of is the brake booster but not sure what other people think or know. any help?