Engine overheating in traffic: causes and what to do on the spot

Long jams and hot afternoons are hard on the cooling system. An engine that overheats badly can warp the cylinder head, so act at the first sign.

If the temperature gauge climbs

1. Switch off the air conditioning and turn the heater to full hot with the fan on high. It feels wrong but pulls heat from the engine.
2. If it keeps rising, pull over safely and switch the engine off.
3. Never open the radiator or reservoir cap while the engine is hot. The coolant is under pressure and can cause serious burns. Wait at least 30 minutes.
4. Once cool, check the coolant level and look for leaks under the car.

Common causes

• Low coolant from a leaking hose, radiator or water pump.
• The radiator fan not switching on (a fuse, relay, sensor or the fan motor).
• A radiator blocked by dirt outside or scale inside.
• A faulty thermostat.
• Plain water used instead of coolant, leading to rust and scale.

Prevention

• Use the coolant type in your manual, mixed as instructed, not plain water.
• Check the reservoir level weekly with the engine cold.
• Replace coolant at the interval in your manual and have the hoses checked for cracks.