how do you compress the piston of a rear brake caliper on a 07 pontiac solstice on 2007 Pontiac Solstice

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i do have a tool to press brake calipers back in but the piston will not move back when i try to use it....i do know some pistons need to be rotated when being compressed to go back in but the piston would have little notches in the sides for a diffrent tool witch the piston does not
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If it is stubborn, try a little rust breaker lubricant around piston edge to see if it will break free. Also, you can open the bleeder valve while compressing to alievate pressure on the cylinder.
thank you for your relply i will try the lubricant but caliper is not rusty so im not sure if thats the problem.I did try opening the bleeder also but it didnt move still.On the back side of the caliper the E-brake is connected in to the caliper but i just didnt see that ide have to take all that apart somehow just to change the pads maybe im wrong it just seems alot