Ralph, Front pads are fresh, thick. I did cycle the front calipers thru their extreme piston travel to make sure they did not suffer the same problems as the rear. Actually, I only had one piston on one rear binding. I robbed known good calipers from another car so, I felt to have equal wear and age on the rear calipers, I'd change both sides.
The puzzler is the fact that there is pressure in the line at the MC. This rules out, in my mind, a binding front caliper piston and I would think the rubber hose as well.
I did suffer from the "check valve swollen hose syndrome " at one of the rears. The soft innards of the hose would expand when you mashed the pedal, swelled shut as the pedal was released holding the pressure at the caliper.
Let me re-state that this IS a rebuilt MC from a local parts supplier. Not new. I have another 300D that has a new mc that I may substitute to verify this one is bad. I am able to change 'em in around 15min now.
Thanks for your help.