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Q: Engine temperature shows overheating

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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.

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