Seeing the temperature gauge climb into the red, or steam rising from under the bonnet, is alarming — and for good reason. An overheating engine can cause serious, expensive damage in minutes if you keep driving. Knowing how to respond calmly can save your engine and keep you safe. Here's what causes overheating, what to do the moment it happens, and how to stop it happening again.
Warning signs your car is overheating
The clearest sign is the temperature gauge rising towards the red, or a warning light appearing on the dashboard. You might also notice steam or a sweet, hot smell coming from the bonnet, reduced engine power, or a ticking noise from the engine. Any of these means you need to act promptly.
What to do if your car overheats
1. Turn off the air conditioning and turn on the heater
It sounds counter-intuitive, but switching your heater to maximum draws heat away from the engine and into the cabin. It won't be comfortable, but it can buy you time. Turn off the air conditioning, which puts extra load on the engine.
2. Pull over safely and switch off the engine
Find a safe place to stop as soon as you can and turn off the engine to stop it generating more heat. Put on your hazard lights. The sooner you stop, the less chance of lasting damage.
3. Wait — do not open the bonnet immediately
Let the engine cool for at least 15 to 30 minutes before doing anything under the bonnet. The cooling system is under pressure and extremely hot; opening it too soon risks a serious scald from steam or boiling coolant.
4. Never open the radiator or coolant cap while hot
This is the most important safety rule. Opening a hot coolant or radiator cap can release a jet of scalding coolant and steam. Only ever check or top up coolant once the engine is completely cool.
5. Check the coolant once it's cool
When the engine has fully cooled, look at the coolant reservoir. If it's low, topping it up with the correct coolant (or clean water in an emergency) may help — but a low level usually points to a leak or a deeper problem that needs fixing.
Should you keep driving?
If the engine cooled down and the coolant was simply low, you may be able to continue cautiously while watching the temperature gauge closely. But if it overheats again, if coolant is leaking, or if you're unsure why it happened, don't risk it. Continuing to drive an overheating engine can warp the cylinder head or blow the head gasket — repairs that cost far more than a recovery callout. When in doubt, call for recovery to a garage.
Common causes of overheating
Overheating almost always traces back to the cooling system. The usual culprits include low coolant, often due to a leak in a hose, the radiator or the water pump; a faulty thermostat stuck closed; a failing water pump that can't circulate coolant; a broken cooling fan; a blocked radiator; or, more seriously, a blown head gasket. Towing heavy loads or sitting in stop-start traffic on a hot day can also push a marginal cooling system over the edge.
How to prevent your car overheating
Most overheating is preventable with routine care. Check your coolant level regularly and top it up as needed, and have the cooling system serviced according to your car's schedule. Keep an eye out for leaks — puddles of coloured fluid under the car are a warning sign. Watch the temperature gauge as a habit, especially in hot weather or heavy traffic, so you catch a problem early. And if a hose looks perished or a warning light appears, get it checked before it leaves you stranded.