Rebuilding my rear calipers on a Formula. Has about 115K on it. They were functioning ok as far as I could tell. So just new seals and cleanup. Should I take apart the internal piston? No oil was noted leaking internally and the E-brake did work. I do have the internal seal coming for it just in case. Any place to get the external slider dust boots beside TFS or Ebay? Thanks Chuck

If the parking brakes works then Do Not take the piston apart for any reason. might be good to rinse inside where springs etc work in w/ new fluid to remove old old fluid and crap in there. Do not put anything in the pad side vent hole.

Rear pistons was never design to rebuild and not even GM Dealers have any data for doing so in FSM and other GM doc's for Fiero and several other car lines.
If you follow BS that claims you can rebuild the pistons on YT PFF etc then you better have good insurance and pray.

And Do Not Hone the bores. Honing can create more problems for aluminum caliper bodies. Bores Do Not touch the Pistons in disk brakes so just remove crap stuck on the bottom of bores.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

I about figured as much. Will flush as suggested. The dust covers on Ebay are from the TFS anyway. Thanks