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uk Transport & mobility emergencies engine temperature warning light • engine overheating after stopping • car overheating pulled over • coolant warning light stopped • steam from bonnet stopped • temperature gauge in red stopped • car overheating in traffic • car overheated on motorway shoulder • broken down after overheating • radiator cap when hot • coolant reservoir check • overheating smell after stopping • car losing coolant suddenly • engine hot light came on • engine heat warning parked safely • dashboard thermometer symbol • overheating after long drive • coolant low warning stopped

What to do if…
the engine temperature warning comes on and you have pulled over safely

Short answer

Switch the engine off and let it cool fully before you open the bonnet or touch anything in the engine bay—hot, pressurised coolant can cause serious burns.

Do not do these things

  • Do not open the radiator cap or coolant/expansion tank cap while the engine is hot, steaming, hissing, or likely pressurised.
  • Do not restart the engine “just to see if it’s fine” while the warning is still on or the gauge is high.
  • Do not pour cold water onto a hot engine or into a hot cooling system.
  • Do not stand on the traffic side of the vehicle or put passengers at the roadside edge.
  • Do not keep driving if the warning returns or the gauge climbs again—stop and get help.

What to do now

  1. Lock in roadside safety first (especially on motorways). Keep hazard lights on. If you can leave the vehicle safely, exit by the left-hand side (furthest from traffic) and wait well away from the car, ideally behind a safety barrier. If it is not safe to exit (for example you’re stopped in a live lane or an unsafe position), stay belted in with hazards on and call 999.
  2. Switch the engine off and wait for it to cool. A common minimum is at least 30 minutes; longer is safer if it was very hot or steaming.
  3. Only when things are calm and cool, open the bonnet carefully. If you still see heavy steam/smoke or hear strong hissing, stay back and keep others back.
  4. Check the coolant level in the expansion tank (not the radiator). Look for the MIN/MAX marks and obvious signs of a leak (puddle, wetness, crusty white staining) under the front of the car.
  5. If coolant is low and the engine is fully cool, top up only if you can do it safely and confidently. Use the correct coolant if you have it. If you have no coolant, plain water is sometimes used as a temporary top-up only with a cold engine—but if the reservoir was empty, you suspect a leak, or you’re unsure, skip this and get professional help.
  6. Use UK help channels rather than risking another overheat. If you’re on a motorway and near an emergency roadside telephone/SOS phone, use it to get advice and assistance; otherwise contact your breakdown/recovery provider. If the warning returns after any top-up, do not drive—request recovery.
  7. Write down the key details for the call-out. Warning light/message, gauge position, any steam/smell, how long you waited, and whether coolant was low.

What can wait

  • You do not need to diagnose the cause (fan, thermostat, leak, water pump, etc.) at the roadside.
  • You do not need to pick a garage, approve repairs, or talk costs while you’re still in a vulnerable place.
  • You do not need to decide whether it’s “serious” right now—treat it as serious until checked.

Important reassurance

This warning can feel frightening, but you’ve already done the most protective thing by pulling over safely and stopping. Cooling the engine and avoiding the coolant cap prevents the most common injuries and helps avoid making damage worse.

Scope note

These are first steps to stabilise the situation and avoid common mistakes. Whether it’s safe to drive again depends on what you find once everything is cool and on professional assessment.

Important note

This is general information, not a substitute for a qualified mechanic’s advice. If you feel unsafe where you are, if you cannot stop in a place of relative safety, or if you suspect fire, prioritise personal safety and call emergency services.

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