What to do immediately
- Turn off the air conditioning and, if the engine is still overheating, turn the heater and fan to full — it draws some heat away from the engine.
- Pull over safely as soon as you can and switch off the engine.
- Do not open the radiator or expansion-tank cap while the engine is hot. The coolant is under pressure and can cause serious burns.
- Let the engine cool for at least 30 minutes before checking the coolant level.
- Look under the car for fresh leaks — coolant is often green, pink or orange and smells sweet.
If the temperature warning came on together with an oil warning, or the engine lost power or made knocking noises, do not restart it. Arrange for the vehicle to be recovered.
Warning signs
- The temperature gauge rising above its usual position, or a temperature warning light
- Steam or a sweet smell from under the bonnet
- Coolant leaking under the car, or the level dropping between checks
- The heater blowing cold air when the engine is hot (often low coolant)
- Loss of power or pinging noises from the engine
Common causes
- Low coolant from a leaking hose, radiator, water pump or head gasket
- Faulty thermostat stuck closed, stopping coolant reaching the radiator
- Cooling fan problems — a failed fan motor, relay, fuse or temperature sensor
- Blocked or damaged radiator, including dirt and debris packed into the fins
- Water pump failure or a slipping or broken drive belt
- Head gasket failure, sometimes the result of earlier overheating
When to get a professional inspection
Any overheating should be checked — even if it only happened once. Driving on with an overheating engine can warp the cylinder head and lead to far more expensive repairs.
We pressure-test the cooling system, check the thermostat, fan operation, water pump and radiator, read fault codes where relevant, and send you an estimate before any work is done.
