What to do
- Pull over safely as soon as you can.
- Switch off the engine.
- Never open a hot radiator or expansion cap. The coolant is under pressure and can scald you badly.
- Wait at least 30 minutes before opening the bonnet to check.
Common causes
- Low coolant from a leak: a split hose, radiator or water pump.
- A cooling fan that isn’t working.
- A stuck thermostat.
- A head gasket failure, often with white smoke and milky oil.
When to call us
If there’s steam, a big leak, milky oil, or the temperature goes straight back up after cooling, don’t drive it. We take it to your garage or home. In summer, cars often overheat in queues on the A1, the A47 and at the Cross Keys bridge at Sutton Bridge. See breakdown recovery.
Checking the coolant once it’s cool
When the engine has fully cooled, open the bonnet and find the coolant expansion tank, a plastic bottle with MIN and MAX marks. If the level is below MIN, top it up with the right coolant mix, or with water to get you to a garage. If it’s empty, or you can see coolant leaking under the car, don’t drive it: the engine will overheat again within minutes.
Preventing it
Check the coolant level regularly, and get any small leaks or a fan that isn’t working fixed before summer. Most overheating calls we get happen on the first hot weekend of the year, in queues on the A1 and the roads to the coast.
FAQ
Straight answers
Can I just top up with water?
In an emergency, water will get you to a garage. Get the coolant mix checked soon, as plain water doesn’t protect against frost or corrosion.
Why does my car overheat in traffic?
At low speeds the engine relies on the cooling fan. If the fan or its fuse has failed, the car overheats in queues but may be fine at speed.