Nissan Repair: Brakes, datsun 720, internal spring

Question
I have a 1981 Datsun 720 4x4 pick-up. The front brakes are dragging. I have replaced most of the components in the entire braking system. The problem still persists. It seems pressure is not being relieved from the front calipers. If I bust a brake bleeder loose it frees up. It is also intermitent. I can drive to work in the morning with out the problem, however at times when I return home the front brakes are hanging. After the vehicle sits the brakes free up. Any help would much appreciated.

Answer
It sounds like the internal spring on the master sylinder is hanging up.  If you crack the lines on the master cylinder see if the calipers free up.  If they do it is definately the master cylinder that needs replacement.  If it is not then the calipers are bad.  But, my bet is on the master cylinder.  Oh, also look under the dash to make sure the pedal is not hanging due to a broken return spring under the dash.