Was changing my rear brake pads today and couldnt get the piston in at all. used a c-clamp and that wouldnt budge it. well my friend acciddently got the piston all the way out and now its not going back in at all. I have class at 9 a.m. that i think im missing because i might need to get a new caliper now.
OK - you messed up. Rear calipers have a TWIST in piston, you must use either a special tool to clamp/twist it in, or some pliers and some determination.
If the piston is all the way out, more than likely you will need a new caliper. Take the old one with you and go to autozone/wherever you normally go and get a core refund put towards a new one.
+1!!! The tool sucks ass. A big pair of straight needle nose pliers work the best. It's easiest to do with the caliper mounted and the rotor off. Make sure your parking brake is disengaged and that you have fluid in the reservoir, and the reservoir cap is off, and push and twist that baby back in.