how to free frozen brake piston
 

My '82 240D has a frozen piston. I have tried using air pressure to no avail. I also bought a disc brake piston wrench. I tried it in a good caliper and it will allow me to rotate a free piston. However, it won't even budge the frozen one. Any suggestions short of getting rebuilt caliper?

Looks like your best bet at this point is to start looking for another caliper. You could fill it with water, and freeze it?? Even if you get it out, I bet the caliper will be too damaged to salvage..

We have a brake bleeder that we have welded to a zerk fitting. We install it and use a high pressure grease gun to force the piston out. If that won't do it, throw it away.