Car is overheating / Engine temperature warning light glowing

Continued operation of a car with an overheating / engine temperature warning lamp will cause irreversible engine damage, resulting in huge repair bills. If your car comes equipped with a temperature gauge (in addition to a warning lamp), you will also notice the needle in the red territory. If either of these happens, stop immediately, switch off the engine, and get professional help.

How the engine cooling system works:

Every car has a system that circulates the engine coolant through the engine to absorb heat created by the combustion process and the friction created by moving parts within the engine. The hot liquid is then air-cooled to dissipate the heat, and the process repeats, over and over again. If any component in that system stops working and you ignore the problem, your car’s engine will be damaged beyond repair.

A basic cooling system is made up of the following components:

  • Radiator: The component where coolant goes to cool down. After the mixture of coolant and water has traveled through the engine, it is pumped through the small, thin, flat tubes of the radiator, which are air-cooled. This cooled liquid is then ready for another trip through the engine.
  • Radiator hoses: These hoses are used to move coolant from one component to another. Hoses need to be regularly replaced as they become brittle and crack due not only to heat, but also to pressure in the cooling system.
  • Water pump: The water pump pushes coolant through the system. Most are belt driven, while a few are electric.
  • Thermostat: The thermostat controls the flow of coolant depending on its temperature. When the engine is cold, it holds the coolant in the engine until it is up to temperature. The thermostat then opens and allows normal coolant flow to the radiator, so it can be cooled.
  • Cooling fan: This fan is used for drawing air through the radiator when the vehicle isn’t moving fast enough to force it through naturally. Some fans are electric and some are belt-driven. But all cooling fans only operate when needed. The cooling fan is not in use during cooler ambient temperatures or when the vehicle is running at speed.
  • Fan switch: The fan switch is a temperature sensor that switches the electric fan on and off.

Possible Root Causes for Engine Overheating:

The most frequent root causes of an overheating engine are:

  • Low coolant: Your engine relies on coolant to dissipate heat. If you don’t have enough coolant running through the system ­­due to leaks, ruptured hoses, loose hose clamps, whatever heat will build up, and your engine will overheat. So check the coolant level regularly, make sure the ratio of water to coolant is correct per your owner’s manual, and have it changed every year. If the coolant is low, do not just top it off and forget about it. The cooling system is sealed and the coolant had to go somewhere. It may have leaked outside the engine and you just can’t see it yet or it has leaked inside the engine where you normally would not see it, but it had to go somewhere.
  • Faulty cooling fan: The cooling fan draws air through your radiator when your car isn’t going fast enough for air to pass through it on its own, such as in slow-moving traffic. A simple way to diagnose whether there is a problem with the fan is to let your car idle long enough to heat up. Then, look under the hood to see if it is running. If it’s not, get professional help immediately.
  • Faulty thermostat: If your car regularly overheats at highway speeds, have the thermostat checked by a professional. But at highway speeds, your engine is doing high rpms (revolution per minute), and needs a working cooling system to keep it cool. If the thermostat doesn’t open, not enough coolant will flow through the engine to keep it cool.
  • Clogged coolant passageways: Your car’s radiator and cooling system need to be clean to be cool. Over time, the radiator builds solid deposits that can clog it and prevent the coolant from circulating properly. A quick, inexpensive radiator flush every year can keep the system in shape.