Can I reuse these caliper pistons?

[elflamo]

Hi all, on my endeavour of rebuilding my S calipers, I found some pitting on the pistons. It seems that the pistons have some sort of chrome plating to prevent them from rusting or?? It is this plating that is pitted in some areas, but all on or just before the internal seal (on the 'outside'). Is this a bad thing, in the pics I'm showing all the pitting on one piston. There wasn't much rust caused by this, but I guess I risk leaking calipers?



Many thanks in advance.

Dennis

[Early_S_Man]

Dennis,

The pitting in both pics is bad enough to tear up the rectangular cross-section seal used to seal the piston to the caliper body. I don't believe very much service would be useful before such leaks became dangerous!

The usual answer is a set of stainless replacement pistons.

[elflamo]

Ouch, off we go again to the webshop....

As my other caliper is already completed (new seals and the terrifying dust caps), did anybody replace the pistons without taking the dust seals out (provided they are new/in good condition). I guess compressed air will have no issue with the pushing the pistons past the dust boots?

Dennis

[Dixie]

Here’s the key question. Did the pistons leak before the rebuild?

I ask because that pitting appears to be pretty far down on the pistons. Personally, given that caliper kits are so cheap, I’d give it a try. Rebuild them, Then put them through the paces on your favorite desolate piece of asphalt. See if they leak. If they leak, you need new pistons. If not, you’re good to go.


YMMV

[Early_S_Man]

Here’s the key question. Did the pistons leak before the rebuild?

I ask because that pitting appears to be pretty far down on the pistons. Personally, given that caliper kits are so cheap, I’d give it a try. Rebuild them, Then put them through the paces on your favorite desolate piece of asphalt. See if they leak. If they leak, you need new pistons. If not, you’re good to go.

Bad advice, IMHO! Waiting to see if it leaks is not my idea of prudent decision-making when examining used caliper parts ... my criteria for reusing caliper pistons rusted in the critical 1/3 'working area' is -- if the rust can be removed with Scotchbrite and you can't feel any pitting with a fingernail, then reuse that piston!

[84toy]

They are not usable. Toss em.....

[elflamo]

Bummer, they have now been promoted to keep the paper down on my desk. They were not leaking at all before the rebuild and the car got through it's annual MoT just fine. Anyway, I think I will take the plunge and go for the stainless ones 'now that I'm in there'.

Thanks for all the responses, wish me luck with the horrifying dust boots (will try the freezer approach!!)

Dennis

[bavaria911]

Forget the pistons. It's not worth the worry and a safety risk at best. Spend the $200.00 for new SS pistons from our host.

Bavaria

[SteveM911]

Don't think I would feel comfortable driving the car knowing the brakes might not work when called for, its just not worth the risk for that sort of money.

[Dixie]

Correction: Early 'S' man is right. I'm looking at the piston up-side-down. I was thinking your "outer 1/3" was the part without the pits.