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.

A: Hi, thanks for writing in. I’d be happy to ...

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: have code p0017 dealer is telling me i need a new engine is this because they dont know what to do next to my car .?

As you may have already learned, the code p0017 indicates an issue with the crankshaft position sensor. This would mean that that transmission doesn't understand the speed and can't send the same information to the transmission. I don't think your...

Q: Mazda not starting.

If your engine is cranking over at a normal speed but not starting, your battery would likely not be the cause of the no start condition. If your car is not cranking at all, then yes, a battery with low...

Q: Transmission replaced, but still slipping - 2009 Kia Borrego

There's a lot going on here. As far as the transmission concerns, your repair should be under warranty since you had the work done at the dealer. For the rest of the concerns, you may want to hire another technician...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
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...