The Symptoms and Causes of Engine Overheating

Engine overheating

There are several signs that can indicate that your car's engine is overheating. If you think your engine is overheating, it's important to pull over right as soon as it's safe to do so and identify the cause of the overheating. If you're unable pull over safely, you should turn off the air conditioning and turn up the heat to the maximum setting.

Signs Your Engine is Overheating

  • The temperature gauge on the dashboard is higher than normal and into the red zone
  • The check engine light and/or engine temperature warning light are staying on
  • There is white or black smoke coming from the exhaust pipe when accelerating
  • The air conditioner has stopped working
  • Fuel mileage has decreased
  • The cooling system is boiling over causing coolant to leak out

Locating the Cause of Engine Overheating

Coolant leak

The most common cause of engine overheating is a coolant leak. A vehicle cooling system circulates coolant through the engine to absorb heat. The coolant is then sent to the radiator to dissipate the heat. If the cooling system has a leak and the coolant level drops too low, it will be unable to remove heat from the engine, and it will start to overheat.

If the coolant level drops too low you will see a warning light on the dashboard. You may also notice coolant leaking under the vehicle, or smell coolant when inside or near the car. When the car engine has been off for 15-20 minutes, check the coolant level to ensure it's within the normal level. If it's empty or extremely low, have the car inspected by a qualified mechanic before running the engine.

Radiator Fan

The radiator fan works with the radiator to cool the hot coolant in the radiator and keep it at a safe operating temperature. Without a working fan the radiator will be unable to effectively cool the engine and it will quickly overheat, particularly when driving at lower speeds. When the engine is idling, check that the fan is turning and operating correctly.

Engine Thermostat

The thermostat's job is to manage the engine temperature by controlling the flow of coolant to the radiator until the engine reaches a predetermined temperature. It allows the engine to warm up efficiently, then maintain a safe operating temperature once the thermostat opens and allows coolant to circulate.

A broken thermostat will either be stuck in the open or closed position. Signs of a broken thermostat include a heater that no longer blows hot air. If the thermostat is stuck open the engine may not warm up and could run colder than normal. If the thermostat is stuck in the closed position it will cause the engine to overheat because the coolant will not circulate between the radiator and the engine.

If your engine is overheating, or you have coolant leaks, a check engine lights that stay on, or other signs of cooling system problems, make an appointment to have your vehicle checked as soon as possible.


Parkway Auto Care
1581 Ford Pky St Paul, MN 55116

Phone: 651.698.3208
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