1997 C2500 LR brake keeps locking up

[SSBrian]

I have a 97 C2500 Chevy, with drums. When I bought the truck a year ago, the brakes were shot and both sides were nearly locked up in the rear. I put new shoes and drums on it and kept having issues with the left rear locking up, I could get under the truck spin the adjuster in and it would be fine for a couple days, then lock up again. So I replaced all the springs, adjusters, and hardware on the rear both sides. It seemed to be fine for about 6 months and roughly 1500 miles. I went to lunch from work today and it was fine, parked it, then when I went to leave at night, wouldn't move, left rear locked up. Turned the adjuster in to get the drum off and checked everything, which all looked good. Any ideas why it keeps adjusting itself out until it locks up going forward, but seems to move fine in reverse?

 

[Ironhead]

I gotta think that there are only two reasons this could happen: The first is that there's a problem with the assembly of the adjuster. I know it's a PITA, but maybe you can take the drum off, and remove the adjuster arm thing that moves the starred wheel at the bottom. If the brake does not lock up after that, you've found the problem.

The second is that something is holding the piston(s) in the brake cylinder out. Could be the flex hose, but that would likely make both brakes lock up. So maybe it's a problem in the cylinder itself. Again, painful, but maybe it's time to disassemble that brake, remove the cylinder, and check the walls for corrosion.