Skip the auto shop - Our mechanics make house calls

Q: White goo/gunk under radiator cap

asked by on

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Need a new pan, lug, gasket.

Hello. It is never recommended to drill a new hole in your oil pan although many have done it. The best recommendation if your oil drain plug is stripped out is to replace the oil pan. It is an extreme...

Q: Car lost power

Hello. Most of the time when this car suddenly stops like this it is because the timing belt broke. If it has never been replaced then this is very likely. It can also occur if the ASD relay failed or...

Q: 2011 Kia Soul Automatic can move the shift lever from D to N without using the thumb button on shifter, is this normal?

Yes it is normal for many vehicles to be able to do this.

Related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...