I'm doing a brake job, and the piston in the caliper is frozen. To make matters worse, the pads have worn a groove in the rotor, and I can't just pull the caliper off (It's "hooked" to the rotor). I can't take the rotor off with the caliper in place, so I'm kind of stuck.

I think I'm going to have to use a pry bar to muscle off the caliper, probably breaking the pads.

Anyone have tips for loosening a frozen caliper piston?