A car engine overheats when the cooling system is unable to absorb, transport, and dissipate heat from the engine. Overheating can lead to severe engine damage, so it’s essential to understand the causes and prevention methods.
Causes of Engine Overheating
Overheating can be caused by several different problems, including:
- Low coolant level – If coolant hasn’t been topped up regularly or is leaking from an external or internal source, the engine will overheat.
- Fan failure – Whether the cooling fan is electric or belt-driven, if it stops working for any reason, overheating will occur.
- Faulty thermostat – The thermostat opens and closes in response to temperature. If it fails to open, coolant cannot circulate, and the engine will overheat.
- Clogged radiator – If the radiator becomes clogged with insects, rust, or other debris, it will not circulate air properly, causing overheating.
- Restricted exhaust – If the catalytic converter on an exhaust pipe has been crushed, exhaust flow away from the engine becomes restricted, leading to overheating.
What Happens When a Car Overheats?
When a car overheats, it can cause major damage to your engine. Results of overheating can include:
- Damaged rings, pistons, and rod bearings.
- Piston scuffing, which damages both the pistons and cylinders.
- Loss of compression due to sticking exhaust valves.
- Blown head gasket, causing compression leaks and coolant leakage into the cylinders.
- Seized or broken overhead cam.
The damage from an overheated engine can be extensive, often resulting in costly repairs. If your car shows signs of overheating, stop and allow it to cool down immediately to prevent further damage.
What to Do When a Car Overheats
If your car overheats, stop immediately. Continuing to drive can cause permanent damage to the engine. Follow these steps when overheating occurs:
- Park your car and turn off the engine. Let the engine cool down—idling will only make it hotter.
- Open the bonnet to allow air to circulate, but DO NOT open the radiator cap until the engine has cooled down completely to avoid scalding yourself.
- Check the coolant level when the engine is cool. If it’s low, top it up. If you don’t have coolant, you can use tap water temporarily but ensure the cooling system is flushed later.
- Inspect for leaks around and under the engine bay. If there’s no obvious leak, such as a burst radiator hose, call for a mobile mechanic. Avoid driving to the nearest service station, as it may cause further damage.
How to Prevent a Car from Overheating
Regular maintenance of your car’s cooling system is the best way to prevent overheating. At the very least, check the coolant level periodically and top it up as needed.
If you’re comfortable working on your car and are experiencing intermittent overheating, try these steps to identify the cause:
- Check the thermostat – Run the engine and feel the upper radiator hose to see if it gets hot, indicating that the thermostat is opening correctly. Alternatively, remove the thermostat and place it in boiling water to check if it opens. If it doesn’t, replace it.
- Check the head gasket – Run the engine and check the exhaust. If white steam is coming out, your head gasket may be leaking.
- Check the cooling fan – Look for oil around the fan clutch or check if the fan wobbles or spins freely when the engine is off. This could indicate a faulty fan clutch.
- Check belts and hoses – A slipping belt may prevent the water pump from working properly, and a collapsed radiator hose may restrict coolant flow. Replace these as necessary.
- Flush the radiator – Back-flush the cooling system to remove rust and scale buildup. Be aware that any time you open the cooling system for service, you’ll need to purge air pockets from the system, as they can cause overheating. Use the bleeder valve on most cooling systems or temporarily loosen a heater hose to release trapped air.
By following these steps, you can prevent overheating and ensure your engine runs smoothly.
