Brake caliper piston lube

[pmbrunelle]

So when I took apart my Cadillac Seville caliper, I found a bunch of rusty sludge in it.

Nastiness.JPG (221.98 KiB) Viewed 4134 times

Caliper materials (not sure about the relevancy, but here it is):
Bore: cast iron
Piston: chrome-plated steel

Brake fluid: DOT 3

Back in the day, I had assembled this with brake fluid as lube to help insert the piston. So after just a few years (less than 10), this happened.

Apparently, for a long-lasting caliper, one is supposed to lubricate the bore with some sort of silicone grease... this is supposed to help keep the corrosion at bay.

What is the correct product to use in a caliper piston bore?

I have some Eze Slide on the shelf, which is a silicone grease, meant for caliper sliding pins. Don't know if it can be used in a piston bore.

I am wary of using silicone grease, because of the warnings of mixing silicone DOT 5 brake fluid and regular DOT 3... I don't know if this matters or not.

[The Dark Side of Will]

Same brake fluid for 10 years? That may be part of the problem.

[pmbrunelle]

Timeline looks roughly like this:

Year 0: Fluid flushed (first use)
Year 2: Fluid flushed
Year 4: Fluid flushed
Year 6: Calipers removed from car, and left in the shed, exposed to humidity. Fluid port left open to atmosphere.
Year 10: I opened up the calipers and found this.

Maybe just with annual fluid changes and a closed system there wouldn't have been a problem.

[Honest Don]

Year 6: Calipers removed from car, and left in the shed, exposed to humidity. Fluid port left open to atmosphere.

This one is the safe bet.

[pmbrunelle]

I ordered a remanufactured Cardone caliper for parts.

When I took it apart, I found a thin whitish grease-like substance coating the bore and the piston.

It felt like silicone grease, but I don't have a positive identification method.

[Honest Don]

When I "rebuilt" the caliper on my CB450, the manual called for lubing the piston and seal with brake fluid. It was printed in the 1970s, so there may be a better method since then.