Skip the auto shop - Our mechanics make house calls

Q: Is this problem the thermostat or blown head gasket?

asked by on

I was driving down the road and my check gauges light came on. I pulled over and my radiator cap was sitting loosely (radiator cap blew off) . It would crank back up (barely) but had a rough idle. I had it towed back to the house. I drained my oil and antifreeze and neither have water or anything abnormal. My buddy said head gasket and another said thermostat. Please help me determine

A: Hey there. Test to see if the head gasket i...

Hey there. Test to see if the head gasket is blown the cooling system will need to be pressurized using a cooling system pressure tester to put pressure on the cooling system to see if it holds pressure. If it does not hold pressure and no external leaks are found then the head gasket is leaking. If no leaks are found the a combustion leak check can be done by using a coolant tester that is held on the radiator opening with a special liquid in the tester that changes to a blue color if engine combustion gas is getting in to the cooling system. This would indicate a head gasket leak or cracked cylinder head. If both of these tests are okay then test the radiator cap and replace the thermostat. If you need to have this looked at by a professional, a certified technician from YourMechanic can come to your car’s location to inspect the potential overheating issue.

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: Can a bad water pump cause water in the oil

Hi and thank you for your question. Water pumps are designed to pump water through the engine, radiator, and heating system. Water pumps will not cause oil to enter the cooling system. The oil coming into the water can be...

Q: Antifreeze is leaking

The best thing to do is to have your cooling system checked to find the cause of the broken tube. The system may have other issues that would need addressed at the same time. That being the case, I recommend...

Q: Thermostat needle going to just past hot side

Hi, thanks for writing in. This is a sign of a faulty or sticking thermostat which is what regulates the coolant flow in and out of your car engine. When this is stuck and closed, it can cause the coolant...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
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...