'07 Cobalt LS, rear drums

I find some slightly sticky brown 'goo' around where this wheel cylinder mates with the backing plate. (Picture below) The other side doesn't have this. I don't find anything unusual on the inside of the backing plate.

I'd appreciate any thoughts on what it is.

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1 Answer 1


Likely it is an amalgam of brake dust and some sort of fluid getting by the seal. Or possibly, brake fluid, though that would be bad and would indicate you are due for new cylinders.

  • Brake fluid would be the issue. But, how would it get (only) there?
    – George
    Sep 21, 2022 at 11:15

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