Skip the auto shop - Our mechanics make house calls

Q: Ovoverheating

asked by on

Replaced upper and lower radiator hoses with new clamps. Replaced thermostat. Drained radiator. When the old upper hose was removed it was dry around thermostat housing. Car still building pressure and overheating. .any suggestions
My car has an automatic transmission.

I am going to have to make a few assumptions here. Number one, I assume your vehicle was overheating before you replaced the hoses and clamps. Number two, the statement you made about the thermostat housing being dry means there wasn’t a leak. If the cooling system was low and the inside of the housing was dry, there is a large leak somewhere that may not have been addressed yet. Unfortunately I am not quite sure what is going on here.

With that being said, I will do the best I can to help you. If there is a leak still, that needs to be fixed before I can be of any help.

A full cooling system that is working properly will build pressure. It is a normal part of the operation of a cooling system. In fact, the building of pressure in a cooling system is by design. The higher pressure allows the coolant to reach temperatures above the boiling point. The boiling point of any liquid changes with pressure. A higher pressure means a higher boiling point. A lower pressure means a lower boiling point.

Assuming the cooling system is full, and the radiator cap is on, the first question I have is how do you know it is overheating?

Is the gauge showing hot? If so, is it working correctly? The best way to see if a motor is really overheating is to use an infrared temperature gun. Temperatures as high as 225 degrees Fahrenheit are normal. Something lower is expected depending upon the circumstances it is being tested. You will need to test several spots to get an idea of the actual operating temperature of the motor. Infrared guns are affected by the color and the material that is being tested.

Under what conditions does the car overheat? When driving? Idling? Up hills or? These are important details to determine what is going on.

As for what could be the problem, if the vehicle was run without coolant for a time, it could have a blown head gasket. As stated before, the building of pressure is normal and is not necessarily an indicator of a blown head gasket. Is there white smoke or steam coming out the exhaust pipe and does it smell kind of sweet? This won’t necessarily happen immediately on start up. When the vehicle is cold with the radiator cap off, put your hand over the radiator hole, attempt to seal it with the palm of your hand while the vehicle is running. If it builds pressure quickly, you likely have a head gasket problem. If not, it still could have head gasket problems. This is just an easy test for badly failing head gaskets. Head gaskets can fail under load only conditions, when fully warmed up or randomly. It isn’t always a clear diagnosis and experience is often what makes the difference.

The next is the water pump. It’s common for water pump impellers to fall off or rust away. Is the cooling system rusty? If so, suspect a rusted off water pump impeller. Either way, testing for coolant flow involves removing a coolant hose to see if coolant will flow out of it. Coolant won’t necessarily shoot out like a water hose, but it might. You are simply looking for evidence of water flow. Ideally, you want to remove one end of the water pump bypass hose. If this is too difficult, remove a heater hose. Remember to do this when the coolant is cool enough to avoid burning you. This process is another one that experience is often the what makes the difference. Remember to rev the motor while doing this test.

Lastly, is the thermostat installed correctly? The pointy end should be installed toward the radiator. Usually there is an arrow on them that points you in the right direction.

Cooling systems can be confusing to diagnose at times. If you find yourself going in circles, consider getting some help from a certified technician who can help you diagnose your overheating issue and get your car running normally again.

Good luck, I hope I have helped you.

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

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: Leak near front passenger wheel possible axle shaft seal

Hello, thank you for writing in. The location that you describe sounds most like a broken axle seal. While it is okay to drive the vehicle for the immediate time, that oil will collect dirt and debris and clog the...

Q: Where is the ambient air temperature sensor located on a 2016 impala LTZ?

There is more than one ambient temperature sensor on your vehicle. The engine air intake system has an ambient temperature sensor located in the air duct after the air filter. That sensor is part of the mass airflow sensor assembly....

Q: Car shaking

The car shaking is likely from a motor or transmission mount, but you could be having other issues, such as an engine misfire. I recommend that you have a mechanic, such as one from YourMechanic, run a diagnostic check of...

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...
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...