I recently notice that my l left side rear pads were dragging and wore the pads down. Upon disassembly, I noticed that the brake pad was not properly aligned in the piston groove and that there was a slight residue on the piston that may have also hindered its retraction into the caliper. I used a little liquid penetrant and flushed it out with clean brake fluid. Its seems to have subsided for now, and hope it does not occur again. Inspection of the Caliper Pins indicated that they were greased and operating properly.

If the rear rotor retracts only by turning it clockwise, how is it that it relieves the pressure from the piston?

I was not looking to rebuild the caliper at this time. However, should I go back in and coat the piston with caliper grease or use liquid silicon brake spray?

Thanks for any suggestions.