Anyone know of any good way to un-seize a rear caliper?

 

disconnect the brake lines and try to pry?

 

Well, the only correct way is removal of the caliper. Then you can secure it in a vice and use a caliper piston removal tool or use the vise itself to attempt to get the piston to move, then use the piston removal tool. Once its out you can use 400 grit or a hone to clean things up, replace seals and rings and reassemble.

 

Wouldn't that mean you have to remove the entire rear disc assembly, not just the caliper??

 

the piston is not seized, the small slide bolt that holds the bracket is seized

 

SO the 2 sliding pins are seized? You still need to take off the caliper and then put in a vice and pull the pins out. Then get some anit-seize compound and lube up the bolts again. Install the caliper and bleed brakes.

 

if i am correct the slide pins are on the pad carrire not the caliper.
undo the caliper and put to one side then remove the carrire. once you have unsized the sliders make shure you take them out and give them a good clean then put some copper grease on them and put back together.