Symptom: Car pulling hard to the right. Left brake pads hard to pull away from the rotor. Right brake pads pull away easily.
Keep trying to push the piston back all the way into the caliper - make sure both pads are in place. If you get the pistons all the way in, then remove the pads and put some worn pads in or possibly pieces of scrap wood about 3/8" thick. Then exercise the brake pedal - run engine for vacuum boost to see if pistons will push out - old pads or wooden spacer will prevent them from coming all the way out (If they do - rebuild calipers)
If the pistons do move out, then push 'em back in again and repeat above. When pushing pistons back in - make sure you pry on old brake pads - do not push on the piston - you could cock it in the caliper bore or ruin the seal.
Repeat as necessary . . .
If pistons begin to leak, time for new calipers . . .
This exercise was used on an old 450SE that had sat for 3 years - recovered brakes to full function with no leaks.