The rear calipers are not just compressed, there is a special tool you need. What this tool does, is it allows you to tighten the piston back. Its actually is threaded, so instead of just pushing it back in, you must screw it back in. I think Autozone loans this tool out w/ a deposit, or you can buy a socket adapter for around 10 bucks.
you can use the c clamp just tighten it slowly
The easiest way is with a "C" clamp.
Remove wheel, remove the two bolts in the calipers, pull up calipers, remove pads compress caliper piston with a c-clamp, be sure to have the brake fluid cap off the reservoir under the hood. - replace pads and reverse the order.
You will need new brake pads, a jack, tire changing tools, various wrenches and a large c- clamp. Jack the car up remove the wheel, remove the two bolts in the calipers, pull up calipers and set out of the way. Remove the pads, compress caliper piston with a c-clamp, be sure to have the brake fluid cap off the reservoir under the hood. Remove the c-clamp, replace pads and put back together in reverse order.
Loosen the bleeder screw then squeeze the piston with a large channel lock pliers or C-clamp. I have a 96 Grand Prix SE and had the same problem....has to be screwed in not pushed in. Take the calipers off & take them to Auto Zone - they will do it for free.
The front calipers push in with a large clamp to pliers. The rear calipers require a special tool that twists the piston while pushing it in.
When compressing pistons on fixed calipers, if the rotor is deeply grooved or if the caliper cannot be removed from the rotor, it's essential to ensure that the pistons are compressed evenly to avoid damaging the caliper or creating uneven wear. In such cases, using a brake caliper tool or a C-clamp can help apply even pressure. Additionally, it may be necessary to clean the area around the pistons and rotor to facilitate better movement. If the situation persists, consulting a professional mechanic might be advisable.
If you are doing the front pads, the bolts to get the calipers loose are either 15MM or a Torx 60. A C clamp to push the piston back in (use old pad to push pistion back in with c clamp.) You need a trustworthy friend to help you bleed the brakes afterward.
Clamp (surgical) Tourniquet (emergency first aid)
If the parking brake is connected to these calipers they thread in clockwise special tool is available (not expensive) at Sears or auto parts If parking brake is not connected to these a "C" clamp should work to retract piston release the bleeder screw then either push them in or use a c-clamp to push them back in... this will waist a significant amount of brake fluid so make sure you have some handy I generally use a "C" clamp, but you can use whatever you have that will put pressure on the calipers to retract. The calipers move slowly and more pressure won't speed the process by much. If the calipers are moving, just keep even pressure on them.
Secret
There not like the front calipers where you put a c-clamp on the piston and squeeze them in, on the rear calipers you have to get a special tool from the parts store and as you push inward you have to turn them in.