If your calipers were anything like mine when I replace all of the seals, you may have one or two pistons refusing to come out. I got three of the four out with piston removal tools. The last one was a bitch refusing to come out even with compressed air pressure. I didn't have a grease gun to use hydraulic pressure using grease so I hooked the caliper up to my brake line and used cars brake system to push the last piston out. Obviously your MC has to be in working order and you have to replace the other piston in the caliper to restore the hydraulic seal