Cadillac Repair: sinking brake pedal, cadillac sedan deville, rear shoes

Question
I have a 1993 Cadillac Sedan Deville. The rear brake line was leaking under the drivers door at the pressure valve. I replaced both of them and repaired the line with new. I bled the entire system from furthest to closest to the master cylinder twice, all air seemed to be out. The pedal sinks to the floor. Still stops the vehicle, but if I pump it up, it works better, but still sinks. The rear shoes have no window for adjustment and the drums spin free, so I assume that is not my problem, but not helping much. Any info would be appreciated. I bled the system with the car running and help pumping and holding the pedal while I cracked each valve.

Answer
Open all the bleeder csrews at all the wheels and remove the master cylinder lid and let the fluid drip from the bleeder screws for 10 minutes while making sure that the master cylinder does not run dry so as to gravity purge all the air out of the system.

You might try bleeding the lines at the pressure valve also.