Rear Brakes STICKING

[HHH_SSS]

I have a 1991 318is I noticed recently that there was a sound coming from the rear end. I jacked up the car and found that the rear pads in the back were sticking to the rotor. I took off the calipers and depressed the pistons back in just to test it out and i put the old pads back in but as soon as i put everything back on and drove the car the brake pads were once again sticking to the rotor. I can still drive the car but its eating my rotors. Does anyone know what could be causing this? Calipers? Brake Lines?

[92BMW318is]

I have a 1991 318is I noticed recently that there was a sound coming from the rear end. I jacked up the car and found that the rear pads in the back were sticking to the rotor. I took off the calipers and depressed the pistons back in just to test it out and i put the old pads back in but as soon as i put everything back on and drove the car the brake pads were once again sticking to the rotor. I can still drive the car but its eating my rotors. Does anyone know what could be causing this? Calipers? Brake Lines?

was this sound like a vacume winding down, ive been having a sound like that comming from the back end, i think it might be the brakes but i am unsure

[dvmotorsports]

I'm guessing you have a bad caliper piston. Probably needs a rebuild or replace. Are both sides doing it, or just one. If both, it is probably another issue as they don't typically fail at the same time.