Did you use the special tool to screw the piston in to make room for the new pads? If not, you probably wouldn't have been able to fit the new ones on over the rotor. The proper procedure is to screw the piston in, assemble the pads and caliper, then use the parking brake to ratchet the piston out so the pads contact the rotor. That will not allow you to over-tighten them.
Assuming everything is assembled correctly, open the bleeder screw to see if the brake releases. If it does, the two things to look at are the rubber flex hose trapping the brake fluid or the fluid has been contaminated with petroleum product. If that's the case, the brake will release if you crack open the steel line right at the master cylinder. Also, the rubber bladder seal under the reservoir cap will be blown up and mushy.
Your rear rubber hoses don't have metal brackets crimped around them where rust can build up and constrict them, but it's still possible for one to tear internally and trap the fluid. The fluid will release at the bleeder screw but not at the master cylinder.
You could simply have a sticking caliper. Ford had a lot of trouble with them in the '70s and '80s but you don't hear much about that now. Be sure the parking brake lever on the caliper is all the way back to its mechanical stop. Ford DOES still have a lot of trouble with sticking parking brake cables but they cause their trouble with drum brakes. With disc brakes, you should still be able to screw the pistons in.
If only the right side pads were worn out and the left side was in good shape, suspect the right caliper or parking brake cable before fluid contamination.
Monday, September 26th, 2011 AT 9:48 PM