Cant bleed brakes. 82 suburban.

I replaced the two piece long brake line that runs from the proportioning valve under the radiator to the rear axle flex line. I,ve tried to bleed the brakes but cant get it to work. pumping the brakes and opening a bleeder routine. The pedal goes to the floor, it will pump up, and slowly sink. Some fluid has gone in by gravity , but it wont bleed correctly. I tried a mityvac on the rears and it wont pull fluid either. There's no other leaks and the brakes were working correctly before I started this. What I,m wondering ,is have I blocked the line by the hitting the brakes with the line off moving the vehicle around. Is there a spool valve or something in the proportioning valve . or master cylinder, or somewhere else. Or should I just try and bleed the fronts too. I haven't opened the fronts. I bought those self bleeders now . I don't think they are going to make a difference , but maybe later they will. Thanks. Verndiesel.