For some strange reason, my rear brake will stick partially closed and then reopen. Any ideas?
A partially plugged equalizing port in the Master cylinder will have this symptom. You apply brake pedal to pressurize the line, the pistons move but when you let up the pedal, the equalize hole doesn't allow fluid back into the Master Cylinder reservoir quickly enough and the brakes drag. Given sufficient time, the pressure gradually bleeds off through the partially plugged port and the brakes stop dragging.
If the hole is completely plugged, the brake dragging heats the fluid and the excess pressure is prevented from releasing to the M/C reservoir which will eventually lock up the brakes.
A partially or fully plugged equalizing port is not at all uncommon particularly if the system has been neglected , i.e not flushed regularly.
Thanks Bucko.