Powdercoater sandblasted inside caliper pistons

So...despite my instructions, they did this: Are they toast?

Oh no, I'd say yes but hopefully I'm wrong or someone can repair the piston surface.

You could try one of these but it might take a while.

@SoCal911t What is that? Edit: Nevermind, found it, it's a bore honing tool.

Once they are done powdercoating the calipers, replace the pistons and seals. There are some really nice stainless steel piston kits. I don't know where to get them, but maybe a Google search will turn up a kit. Really nice upgrade too!

Wow! Not so good. Yes, you need to hone the cylinders then check the clearance between the piston and the cylinder. But first measure the current bore to piston clearance. It may already be too large. Honing would just make it larger. Sorry, I don't know the spec. The bigger problem is what the sandblasting may have done to the seal surfaces. These need to be quite smooth to seal correctly. What a mess. Edited after seeing Joe's post: Were the pistons in the calipers during sandblasting? If yes, I agree with Joe. Replace the seal and boot and you should be good to go.

That's unacceptable and a noob mistake. Have you brought this up with the place that did the work? I would be concerned about putting this back on the car. If you can't seal and hold pressure in the brake system then it's all useless.

Make them buy you new calipers, I would not try to fix them.

GT3 calipers are a grand a piece. I'm most likely going to have to take this place to small claims to get them to pay for that. I fully disassembled the calipers prior to bringing them to the shop except I left the inner seals inside (which is probably a good thing as the sand blasting didn't affect the seal shoulder). They called this morning and said the guy sandblasted the parts and isn't sure which parts to tape off. At that point I rushed over and saw what they did and was pretty pissed, obviously, so I took the calipers home and told them I'd follow up with hem as I didn't want them to monkey it further. Plan was to rebuild them anyway but the question is if the sandblasting removed enough material to make the tolerances off for the pistons. The seal itself is what prevents the fluid from leaking past the pistons. Fully seating the pistons without seals, there seems to be minimal play; however, halfway seated there's play now whereas before, when I popped them out, seating them anything more than a couple mm made them almost impossible to get out.

Off with his head!

No bueno at all. The sandblast itself took away material and left an imperfect surface, honing to correct and return to a proper finish will take them well out of tolerance, if they aren't already. Hopefully the shop will own up to their employee's mistake and pay for replacement calipers, that was a pretty dumb move. If he didn't know what to tape off, probably should have asked for guidance instead of going in blind.

Sorry. My comment was based on I thought the pistons were still in the bores. But now I see that is not the case. Why did you remove all of the pistons? Obviously a very bad mistake. I think you are going to have to find some used calipers as replacements. LA Dismantlers?

Take the calipers back to the powder coater's, diplomatically but firmly inform them that they must replace the damaged calipers even if only with good used ones, and if they decline, immediately file a claim in small claims court. The sooner you file, the sooner this will be resolved. When you gave the powdercoater your calipers a bailment was created wherein the powdercoater has a legal responsibility to return the calipers to you in no less a condition than when they received them. Slam dunk.

To try and “save” them .You could call:white post restorations to see if they can re sleeve them.

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This seems like a good options. Send them out to a professional brake company. Get some more information about their condition. Sorry this happened, but it seems like they were damaged by a person representing the company. The next step is collecting enough data to prove they aren't usable. Brakes should always work reliably. Hang in there,

that really sucks. do they make oversize replacement pucks? maybe some place like this: https://www.autoquestcars.com/custom-08 or https://www.demonspeedmotorsports.co...nts-DSM-CD.htm

I've power coated at home quite a bit and the good news is that it's not that difficult to remove. The bad news is that the Eastwood "Powder Coat and Paint Dissolver" I used seems to be no longer available. I had to remove some wrinkle finish powder coating that didn't come out perfectly, and Eastwood's solvent dissolved it fairly easily. You might want to give Eastwood a call and see if they have a replacement solvent. The video below shows the product in use. I don't know if they discontinued it because of safety issues, but I don't recall it having any noxious fumes at all. You Tube

Its possible they could be professionally honed/machines but I suspect at today's labor rates ,, it ain't worth it. I have been finding lately there are a lot of hacks out there in the powder coating industry, something else to consider, how hot did they bake the powder coat.. if they did the 700 degree bake some exhaust systems get.. that would be bad.

It looks like they have only sandblasted it. (which they shouldn't have blasted the bores). Just send them to Millennium and have the bores Nikasil'd then honed to the stock size, better than new !!!

If it was a reputable or established business, they most likely have a GarageKeeper liability insurance which covers these kinds of expensive damage to customers� vehicles/parts. Replacing with new calipers is your best option. A used set, bcs its condition cannot be ascertained, can be as bad or worse than yours before blasting. Even if you manage to have the bores sleeved or honed, beads or sand particles, under high pressure, can find their way into all nooks and crannies inside the caliper and despite meticulous cleaning, will eventually dislodge and damage your braking system. I remember reading a few years back that Porsche lost a major race (GP or similar) due to complete engine failure on all 4-6 cars entered, which was later diagnosed as the residual sand-casting sand particles having dislodged themselves. Failures of brakes, tires or steering system can be catastrophic (i.e., deadly.)

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This is good advice. I owned a couple of franchise auto shops and I had to carry garage insurance. The insurance never hassled me if I had to submit a claim. My insurance wouldn't even have blinked an eye at a small $2k claim.

FWIW, I'd Vapor blast calipers,, if I wanted them cleaned.. its way better control and produces a awesome finish.

That surface finish needs to be around 16 Ra. You're going to have to remove material to get to the "bottom" of those peaks and valleys - the bore will likely be out of tolerance (oversized) by the time you remove the "peaks". That being said...what do you have to loose at this point? Let's say you were able to hone the bore and bring the surface finish back into tolerance; the next step would be to do some searching for the actual tolerance of the bore. Should you go this route...do not use calipers for this measurement - you will need a bore gauge. You might get lucky and be on the high side of the tolerance. Racing Break in Fullerton sells rebuild kits with SS pistons - you should try to get ahold of someone there who knows what the bore tolerance is. Edit: Doubt a bore gauge will fit. Gauge pins will probably be the easiest way to take that measurement.