As part of a preventative (I noticed no symptoms from the driver's seat perspective) brake rebuild, I took apart a set of rear brake calipers.

On one of the pistons, the metal cap is slightly caved in on the edge by about 0.030":


Good to go ahead and use the piston as-is, or replace?

Can I take this apart, and flatten this with a hydraulic press?

This piston is from a Cadillac Seville caliper.

[This message has been edited by pmbrunelle (edited 01-03-2021).]

Likely someone drop the part. Nothing in the caliper should touch the cap except the large spring you see pulling the piston.
Directly under the "cap" is a BB set w/ two thin "washers" as upper and lower races.
See my Cave, Rear Piston notes

Bend the cap can be problems for P-brake and self-adjust as the BB maybe bad.
Taking apart the piston isn't a great idea either even w/ "internet" saying can rebuild a iffy piston. Worse likely some rebuilder already torn it apart 1 to several times weakening the cap.

------------------
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

10-4

I'll get another one.

I couldn't buy just the piston, so I bought an entire Cardone caliper just to cannibalize its piston.

Its cap was slightly dented as well (but much less pronounced), but I just pried it a bit (from the outside, no disassembly required) with a screwdriver so the bearing race sat flat on the cap.

I removed the vent plug from the piston pictured above, and I found that it was wet with brake fluid inside, so I guess it was needing replacement anyway.