Hello and help!!!! Rebuilt entire brake system. Nothing that has not been replaced. Bleeding brakes and onle get fluid from front. Fluid became free of air and clean, quickly. Cannot get fluid from either rear, pedal does not move down when opening rear bleed screws. Pedal does not return to top, when release. About an inch shy of top, but firm. B is a 70 with the dual mc. How do I proceed???? Thanks DennisP