k h brake caliper question

You'll probably have to rebuild the caliper even if you get the piston freed up. There are several methods to remove stuck pistons. Using the master cylinder to move them if the hydrolics are still hooked up, usually works. If you have the caliper already off the car, you can try compressed air but be real carefull doing that as those piston can become missiles! Keep your fingers out of the way and use a block of wood inside to cushion them and keep the pistons from coming completely out on the fly. Another safer method is to use a grease gun on the open bleeder. Makes a mess but will usually break them loose. If all else fails, you can split the calipers apart and put them in a vice to break the pistons loose.