I went to change the rear disk brakes on my 2006 Pontiac Montana last night. When I discovered neither brake caliper would budge. Is there a trick to fixing this or do I really have frozen calipers?
I think one would need to know a lot more about your experience and what you did to try to compress the pistons before being able to say anything.
ABS systems can involve very high line pressures. Did you loosen the bleeder screw in order to compress them? This is safer for your brake system.
If the rear wheels were spinning and if the rotors weren’t covered with surface rust then its very unlikely that your calipers are frozen.
I did not loosen the bleeder screw. Everything looked normal rotors in good shape and turned just fine.
What is your method for compressing the caliper piston? A typical DIY method is with a C-Clamp. I have used a giant set of channel locks. There are also specific tools make for this. Either way, loosening the bleeder screw is a good idea. It will get rid of some old brake fluid & not subject the brake system to the back flushing/pressure. It also makes it a lot easier to put the piston back in.
I’ve been using a 9" c-clamp to compress. Usually works nicely, not doing the job. Tried loosening bleeding screw, no effect other than big mess.
If the rear calipers double as the parking brake, you can’t just push them back. You usually can tell by the face of the piston. There is a screw mechanism for the parking brake to actuate the caliper. You have to screw the piston back in, with the bleeder loosened. Sometimes a special tool is needed to screw it back in, some you can use pliers or mcguyver something. This may or may not be the case, but it is in a lot of cars.
I thought you were trying to compress the piston, but looks like I missed the part that you can’t get the caliper off. Still, it is the parking brake thing. Most cars use the rear calipers for parking brake. Make sure the P-brake is off and the front wheels chocked first.
Are you working with a repair manual?
The pistons probably have to be turned back in with a spanner-type wrench. Some of the big-chain auto parts stores not only sell repair manuals but also have loaner tools. Among those is likely some kind of brake servicing kit.