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・Save up to 30%

Get a quote

What others are asking

Q: Antifreeze coming out

Hi there. It is possible you may need to replace your thermostat. The thermostat opens when the car gets warm to allow more coolant to flow through the cooling system. When it fails, it can become stuck closed and will...

Q: Intermittent overheating

Hey there. This may suggest that the coolant fan relay switch may not be working properly. When you car is moving down the freeway at higher speeds, the engine gets a lot of cooling assistance just simply from the air...

Q: Water in oil from drilling too deep

If you use a good silicone on the bolt when you put thermostat back in you will seal the hole from more coolant getting into the engine oil. Once the oil is flushed out you should pressure test the cooling...

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...
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...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.