OK I just rebuilt the calipers in my Nova. Seems like this is a bit of a lost procedure given the cost of rebuilt calipers. I thought I would go through and show the process I use. Now, this may or may not be the text book method, I don't know. It's the way I've rebuilt hundreds if not thousands of calipers over the last 20 years or so. The GM single piston is about as simple as they come.
Here we have the caliper in all it's unwashed glory. Notice I have an old pad between the caliper "fingers" and the piston. I'd rather not have the piston slam into the caliper.
Using compressed air I'm going to force the piston out of the bore. This is no time to put your fingers in the way. I'll tell you for a fact that hurts really bad.
I use another rag like this to keep the fluid from flying all over. If you have a customer that likes to stand right over you and watch you work this step can be skipped.
The piston pops out.
Pull the piston out. Take a screw driver like this and wedge the dust seal out. You may have to do this in multiple places.
Pull the seal out of the bore.
This one isn't too bad. I've seen a lot worse. Remember nothing seals in the bore. The o-ring we pulled out of the groove seals on the piston Get it clean but don't stress over perfection. Some of the stains will not come out. As long as it's smooth you are good. Get the groove very clean.
The piston is fairly bad, but will clean up.
A little brake clean, elbow grease and a scotchbrite pad and we have a usable piston again. You can use krocus cloth or if you're careful a wire wheel. It has to be smooth. Any pitting or groves means you need to replace it.