240 stupidly sandblasted ATE caliper

I was cleaning up a set of rear calipers from a 1993 240.


I was sandblasting and stupidly "lightly cleaned" the receiving cup for the piston.



Any opinion on whether they are runied?

Not ruined, the piston has the finish that is critical.
Be sure to get the seal groove clean.

Maybe run a small hone through it? I'm no expert so use my advice at your own risk

Just get a brake hone and hone it.

Its what the rebuilders do anyway.

You don't hone brake calipers!

To rebuild you media blast the caliper and replace the piston.

So long as they're not too pitted I'd run them. My 960 rear brakes were seized from rust, with very light pitting on the bottom. It's been at least 10k since then and no visible issues. The hardest part is getting those dust boots on. I installed the Piston seal, then the boot with a collar to hold it wider then the Piston then just drop the Piston in. I think the collar I used was the outer ring of a spray paint lid. Good greased slides should keep the Piston from dragging the bore for the most part anyway.

Thanks. After some more research, i found out about the brake hone, got one, and they seem perfectly smooth again.

Dirty Rick said:

You don't hone brake calipers!

To rebuild you media blast the caliper and replace the piston.

Click to expand...

Actually, you do, if they are corroded. glass beads embed in the surface, and will wear out the seals. Honing and cleaning will fix that. (honing without cleaning is juju)
If the pistons are pitted or flaking you replace them. If not, wire wheel and re-use.

And do NOT use vaseline like these knuckleheads suggest. ANY petroleum product on brake seals, boots, etc. is also bad juju.