I am in the process of changing the brake pads on my 87 4-Runner. It has the S12+12 calipers (4WD IFS 4-piston). I got the driver's side completed so far. However, the top front piston on the passenger's side will not go back into the caliper. It moved in only a fraction of an inch and will not move any further. The other 3 went in fine. I tried removing brake fluid from the system and then tried taking the caliper off and using a C-clamp however that did not work either. I pulled the cylinder boot and set ring and tried to remove the piston but I can't figure out a good way to pull it out. Any information on this subject would be greatly appreciated. Anyone have any experience rebuilding these calipers? This happen to anyone else? I need this thing back on the road by tomorrow.