You cant push the piston on your rear brakes back in my 02 Volvo s40?
To push the piston of the rear brakes, first, use a large, flat-head screwdriver to pry the retaining clip loose at the top where the caliper meets the brake cylinder housing. You might need to pry in multiple locations to ensure even release from any rust. Once the retainer spring pops off of its mount, you slide it sideways and out of the way completely. With the retaining spring removed, a large adjustable wrench with an open end and straight end may now be slid over the cylinder housing in back. Use the adjustable wrench in the direction to turn the cylinder back into the caliper while you push gently but firmly against the center of the brake cylinder’s black rubber boot. As soon as you see and feel the cylinder moving inward some, and feel less pressure/resistance with the adjustable wrench.