Caliper pistons are crumbling?

Replacing my struts today and found this. The caliper in question is the RF. I apologize, the pictures aren't the best, but it looks and feels like the caliper pistons are crumbling. When I took the caliper off a bunch of rust powder fell out of the pistons. The bottom of the pistons feel like they are bulging outward and there is some deep looking cracks forming in the area where they are bulging. I looked at the other front caliper (which is brand new as of last week) and the pistons are flat, no bulging or anything. I'm worried that one day the pistons might bust open during braking. My gut is telling me to just replace it but I hate to replace a factory caliper because the re-man caliper on the LF recently froze after just one year and 10,000 miles. The only other thing I can think is that a few layers of rust are working loose, giving it this appearance but I hesitate to pick at it. Has anyone seen this before?

 

EDIT: Third picture is one I found on the internet, apparently from a Honda Element. Mine don't look quite as severe as that and they're not leaking fluid but it's a good pic of what I'm talking about.

I have an older forester and an older outback that both have that condition inside the caliper pistons. I knock the stuff loose with my finger and dump out the rust. But as long as the piston is working correctly/not leaking I don't believe it's an issue. I've had the outback for over 3 years with this condition and the brakes still work fine.

Worst case scenario, but unlikely, is that they burst and that caliper stops working making you loose fluid and pressure in that line. Not all that dangerous since this will only affect two wheels. the one that ruptured and the opposite one (side and axle wise).

 

Replacing the pistons will probably give you a better brake pedal feeling and these pistons might also not be returning as they should because of rust on the outside as well.

 

It might be cheaper to get used calipers on a junkyard than replacing the pistons and seals though.

Update: I went ahead and picked up a re-maned caliper with bracket, pins, and clips for $65 at Advanced Auto Parts. This is the same kind of caliper that I just installed on the driver's side a week ago. At least now both my front calipers will match:lol:. There is no core charge on these calipers so I will disassemble it and see how thin the pistons really are. Will post back with my findings.

So you got remanufactured caliper at advanced auto parts? Did you go to the store or did it online?

 

One of mine is in really bad shape so need to find something soon

Is there anything that can be added to protect the interior of the pistons from rusting? Maybe anti-seize?

If I could get it clean enough, I'd paint it. If not, a light coat of sil-glyde (or is it syl-glide) or other brake lube.

Hey all, sorry for the late reply. I've been busy with school and addressing other overdue repairs on my car so I haven't yet taken the pistons out of the old caliper but I did pick at it and got large chunks out which were a little wet underneath which makes me think the pistons were "seeping" brake fluid a very little bit. I de-greased and painted the new caliper and bracket with silver Duplicolor caliper paint (making sure to mask off the pistons and seals).

 

vlad_b,

I got the caliper at Advanced Auto Parts. iirc it was around $65 for the caliper with bracket and new springs/shims. There was no core charge for the caliper either.

 

theflystyle,

What I did was I spread a thin film of Nissan PBC brake grease on the inside of the pistons on the new caliper, HOWEVER, make sure to wipe the dust boot completely clean of grease. Any grease left on the dust boot could attract dirt which could abrade the boot and lead to premature failure of the boot. I'm sure any brake grease would work but I found the Nissan stuff is really good. If you look at the ingredients it's basically anti-seize that's been formulated to withstand high temperatures. It doesn't get washed away and it doesn't harden or dry out either. My dad's friend used it to lubricate the weather vane on top of his barn and it's been moving trouble free for something like 5 years now. I don't know what it costs at the dealer but it's on Amazon for $42.

I like this idea, thank. I sprayed my rusty looking pistons with Krown rustproofing, but something high-temp would've been better.