Calipers are
so easy to rebuild, everyone with a source of compressed-air should try it. Multi-piston calipers or aluminum-body calipers are somewhat more difficult, but still pretty easy.
My own cars get the calipers pulled apart, cleaned-out, and shoved back together. I don't even buy seal kits for 'em. It's a zero-dollar overhaul other than the time I spend, some electricity for the wire wheel, and some anti-seize and brake fluid.
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Scuzz on the square-cut seal, partially peeled-off with my fingernail. Aluminum calipers will need the seal groove cleaned out with a pick or other implement.
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The fit between the caliper bore and caliper piston is so loose that "scoring" of the caliper bore mostly doesn't matter. The PISTON has to be pristine below the dust-seal groove, though. No flaking chrome, no scoring, no dents.
I had a black-coated (NAPA) caliper almost certainly sourced from Cardone that came on my '97 Plow truck. The black coating was coming off. Not real impressed. Someone--the rebuilder, or maybe someone after that--had shoved a bleeder-screw "repair kit" into that caliper. The bleeder screw on the repair kit broke, and I didn't have a receipt for the "Lifetime Warranty" so I had to buy another caliper.
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I made sure that the replacement, black-coated "rebuilt" caliper DID NOT have a bleeder-screw repair kit in place!