Q: White goo/gunk under radiator cap

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A/C wasn't working this summer. Changed thermostat. Air working. Recently flushed radiator, and noticed a white gooey substance on cap and in fluid. Car does not overheat, and cabin heat working fine. No signs of leaking externally. Also changed radiator cap. Not sure what to do with this.

My car has 104000 miles.
My car has an automatic transmission.

Hi, thanks for writing in. I’d be happy to provide my insight.

This is often times a sign of a blown head gasket, however if this were the case your car would be overheating. I would recommend checking the oil in your car to see if it looks milky or has a white color to it or any signs of water. Also, check the coolant to be sure you do not see any signs of oil in it. If either of these are true, you may have a blown head gasket.

If you would like help, consider having an expert automotive technician from YourMechanic come to your home or office to inspect this substance for you, and make or suggest any repairs as needed.

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