Rear brake locks up when ebrake is pulled.

[blacsti]

Hey guys ive had this problem for a while now and cant seem to fix it. It seems like something that should be obvious but im not getting very far,

My car:
1995 240sx with manual trans swapped. j30 vlsd, q45 front calipers.
i have two hardlines coming out of the MC that go to each front caliper, meaning ABS if im correct?? not too sure.

Problem:
The right rear brake locks up while driving, its done it a few times and pressure releases after opening the bleeder. I can open a bleeder on either side rear caliper, and the MC bleeder also does the trick.
No matter how long it sits the pressure holds until opening a bleeder.
Replaced the right rear caliper and the problem still persists.
The left side seems to be fine, because before it would lock up and i would use a screwdriver to pry the pads from the rotor on the right side. and then it would roll.
When the car was jacked up in the rear, when pushing the brake pedal and letting go, you still are able to turn the rear axles. But if you put the ebrake up and then let it down, the rear wheels are stuck and you must open a bleeder.
SO, it seems the brake starts locking up slowlly while driving, and when pulling the ebrake it locks up much quicker.

Ive replaced the right rear caliper, the hardlline to caliper hoses on both sides. Ive checked for any blockage in ALL the hardline and its all fine.
Ive disconnected the ebrake cable and the problem still persisted.
The pedal seems to be adjusted correctly.
The fronts do not lock up.
ebrake cable seems to move fine as well.

any thoughts?

[roboticnissan]

Your master cylinder sou.ds bad.