I have a 03 civic ex replaced radiator thermostat still overheating and the last time it overheated I got a greyish sludge come out of the radiator cap. Can someone help?

  • You could consider flushing the system - to remove any impurities / sludge which sounds like is in there.
    – Solar Mike
    Jul 28, 2018 at 17:41
  • Welcome to Motor Vehicle Maintenance & Repair! How does it behave when it's overheating? I mean, are you basing the overheating diagnosis off of what the dash gauge says? When it does overheat, is it "okay" then all of a sudden spikes up to well over normal temperature? Does the radiator itself boil over? What happens? Jul 28, 2018 at 17:51

1 Answer 1


if "greyish sludge" is what I think it is, you blew a head gasket when you overheated it. The greyish sludge is motor oil. It sludges when mixed with antifreeze

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.