What Should I Do if My Vehicle Is Overheating?

By Karen Johnston June 28, 2019

Quick facts

A sweet syrup smell near your vehicle often indicates a coolant leak from the cooling system.
Aluminum cylinder heads can warp permanently from a single severe overheating event.
Coolant entering the oil passages causes catastrophic lower-end engine damage.
An inaccurate temperature gauge reading can occur when coolant level is too low to reach the sensor.

If the temperature gauge enters the red zone, warning beeper sounds, or you notice coolant leaking, smoke from under the hood, or a sweet syrup smell, pull over and turn off your vehicle immediately.

Cooling System Inspections

Any leak or issue with your cooling system requires immediate attention. The temperature gauge receives information from the coolant temperature sensor, typically located in the radiator or coolant reservoir. A low coolant level means the sensor has nothing to measure, resulting in inaccurate readings. "If you have a coolant leak and are refilling the coolant regularly, you could be overheating your vehicle and not even know it."

Overheating Damage

Overheating risks serious engine damage. Modern aluminum cylinder heads can warp from excessive heat, and the cylinder head gasket between the engine block and cylinder head(s) may blow. Coolant entering oil passages causes lower-end engine damage requiring replacement or rebuilding.

Regular Maintenance

Regular inspections and prompt repairs prevent overheating issues from becoming severe. If your vehicle overheats despite maintenance, pull over, turn it off, and call for a tow. "It's a lot less expensive for a tow bill, than for a head gasket repair or engine replacement due to overheating damage." Make sure to let the repair technicians know that overheating occurred so they can conduct appropriate diagnostic tests.

Happy Motoring!

Frequently asked questions

Common questions

Is it safe to open the radiator cap to check coolant when the engine has been running?

No. The cooling system operates under pressure when warm, and removing the cap while the engine is hot releases that pressure violently, spraying scalding coolant and steam. You must wait until the engine has cooled completely, typically at least 30 minutes after shutting off, before opening the radiator cap or coolant reservoir. If you need to add coolant in an emergency and the engine is warm, let it cool first; adding cold liquid to a hot engine can also cause thermal shock to the cylinder head.

What is the purpose of the coolant temperature sensor and where is it located?

The coolant temperature sensor measures the temperature of the liquid in the cooling system and sends that data to the engine control module, which uses it to adjust fuel delivery, ignition timing, and cooling fan operation. It is typically threaded into the thermostat housing, the radiator, or the coolant reservoir. If the sensor fails or reads incorrectly due to low coolant, the ECM may run the engine with incorrect parameters. The dashboard gauge may show a normal reading even as the engine overheats.

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