Ford Repair: 1984 Ford Ranger Brake Pressure Valve, brake locks, pressure valve

Question
MY 1984 Ranger right front disc brake locks when used. I've replaced calipers, pads, lines and fluid. I'm told that the pressure valve may be the culprit. Can it be removed and cleaned as Ford wants $358 for a new one and they further state that the part is obsolete and cannot be found elsewhere. Please help. I have to move and take my truck with me and have limited cash.

Answer
it very well could be the problem but from what i've seen would be rare
most of the time caliper and line fixes this on the ranger-make sure you have flush all the dirty fluid through the system and brake fluid is clean and not contaminated-if your lines screw into a check valve on the master cylinder (looks like a nut about 1/2 to an inch long) instead of straight into the master cylinder you may want to replace  the check valve-without being able to be there i am still suspicious of that side even though parts have been replaced-