Skip the auto shop - Our mechanics make house calls

Q: Engine temperature shows overheating

asked by on

Driving on hwy temp gauge reading hot engine safe mode kicks in. Replaced water pump and thermostat no blockage in radiator. Temperature gauge reads hot. Heater will not blow hot air. Could it be coolant temp sensor?
My car has an automatic transmission.

A: Hey there. If the heater valve (for the pas...

Hey there. If the heater valve (for the passenger compartment heater core) is working and you do have the heat set to high but there is no heat, there is either trapped air in the cooling system or a physical blockage (which includes the possibility of collapsed hose(s)). Either of those problems would cause engine overheating.

There are air purge points on high points in the cooling system which if you open during refilling with coolant, will help to lessen the possibility of trapped air but even opening the purge points is not foolproof. On occasion, I have only been able to "dislodge" trapped air by swerving while driving and this literally forcing the air to move out and get "trapped" elsewhere at the top of radiator where it will not block flow. Yes, a defective cooling sensor can cause overheating by either failing to actuate cooling fans and/or creating a lean running condition, misfires, and so forth. But that sensor is fairly easy to evaluate with a volt ohmmeter and thus rule in or out (of course just because the sensor works, that doesn't mean the PCM is getting the signal, so the circuit integrity has to be confirmed as well). If you would like to have this looked at by a pro, a certified technician from YourMechanic can come to your car's location to diagnose the overheating issue and follow through with repairs.

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: Truck starts to overheat and blows cool from the heater but fixes itself after hitting a bump.

The overheating may also be caused by other issues such as a bad heater core. This is a small radiator used to warm up the interior of the vehicle making the heater operational. A valve controls the flow of hot...

Q: Exhaust and engine

Hi there: In short; YES, it's very possible to have mechanical damage to internal components by removing exhaust system components on a stock engine. Today's engines are fine-tuned and rely on precise settings to tune a vehicle's air to fuel...

Q: Transmission problems, cannot reverse

Hello. It sounds like the transmission that was rebuilt and installed in your vehicle has failed. Start by having a mechanic take a closer look at the issue. A certified mobile mechanic from YourMechanic can inspect your transmission and shifting...

Related articles

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...
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 P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...