Pontiac Repair: rear disc brakes, rear disc brakes, caliper piston

Question
On my son in laws 06 grand prix GT. He as going to replace rear brake pads but he could not get the piston to back inside the housing. After we took out the bolts the piston kept such tight pressure we still could not get the caliper off. He was afraid to loosen the bleed valve fearing it would interfere with the abs system. How do we get the piston to release Pressure. And any more hints about what to watch for . Thanks in advance for your time.

Answer
Hey DW:

That car need a special tool to retract the caliper piston into the caliper. Right now there is probably a rust groove that is holding the pads up whe n your trying to remove the caliper. A small bar between the caliper and the rotor should pry it off the caliper and over the rust ridge once you remove the bolts. Then take the pads off the caliper and the special tool will rotate the piston back into the caliper. It's on a screw mechanism that hold the piston into the claiper due to the parking brake assembly is part of the caliper. Any parts store should sell the tool you need to do the job. opening the caliper bleeder will not help you out in this instance. Good luck :)