Short answer
If your car is overheating, turn off the AC and set the heater to hot, fan on high. Then pull over away from traffic and turn the engine off. Never open the radiator cap while the engine is hot: the coolant can spray out and burn you. Wait at least 30 minutes, then fill the plastic coolant tank if it is low. If it overheats again, call a tow or a mobile mechanic.
Safety first
Never open a hot radiator or coolant cap. On a highway, turn on your hazard lights and pull as far from traffic as you can. If you see flames or a lot of smoke, get everyone out of the car and well away from it and from traffic. Then call 911.
What to do when your car overheats
1Steam from the hood, needle near H
The temperature needle climbs into the hot zone and you may see steam or smell something sweet. Act now: an engine that keeps running hot gets badly damaged.
Read all the steps
- Steam from the hood, needle near H. The temperature needle climbs into the hot zone and you may see steam or smell something sweet. Act now: an engine that keeps running hot gets badly damaged.
- AC off, heater on full hot. Turn off the AC and turn the heater to hot with the fan on high. It pulls heat away from the engine while you find a place to stop.
- Pull over safely and turn the engine off. Signal, turn on your hazard lights and stop well away from traffic. Turn the engine off and keep the hood closed while it steams.
- Never open the radiator cap hot. The coolant is under pressure and can spray out boiling. Do not touch the radiator cap or the reservoir cap while the engine is hot.
- Wait 30 minutes, then check the coolant. With the engine cool, open the hood and find the plastic coolant tank. If the level is below MIN, add coolant up to the MAX line.
- Still not fixed? Call a mechanic Especially if: the temperature goes back up after adding coolant.
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Once the engine is cool
- 1
Add the coolant your owner’s manual calls for. In an emergency, plain water will get you to a shop.
- 2
Look under the car for green, orange or pink fluid dripping: that is a coolant leak.
- 3
Start the engine and watch the needle for a few minutes. If it climbs again, turn it off and call. Driving it hot can turn a hose or thermostat repair into a much bigger one.
Common causes
- Low coolant from a leak (hose, radiator, water pump).
- Radiator fan not turning on (often overheats in traffic, fine on the highway).
- Thermostat stuck closed (the valve that lets coolant flow to the radiator).
- Failing water pump (it moves the coolant through the engine).
- In older engines, a blown head gasket (a seal inside the engine). Signs: white smoke, and coolant disappears with no leak in sight.
When to call a mechanic
- The temperature goes back up after adding coolant.
- Coolant is leaking under the car.
- White smoke from the exhaust or the oil looks milky.
- The car overheats in traffic but not on the highway (fan problem).
Frequently asked questions
Can I drive an overheating car to a shop?
Only if it is a short distance and the temperature stays normal after cooling down and topping up the coolant. If the gauge climbs again, stop and call a tow.
Can I use water instead of coolant?
In an emergency, yes, to get to a safe place. Have the system refilled with the right coolant mix soon, because water alone does not protect against freezing or corrosion.
Why does my car overheat only in traffic?
Usually because the radiator fan is not working. At low speed the engine depends on that fan, while on the highway the moving air does the job. A bad fan or fan relay (the switch that turns it on) shows up in traffic first.
Why is steam coming from under my hood?
Usually it is coolant boiling out of a leak or the coolant tank because the engine is too hot. Pull over, turn the engine off and keep the hood closed until the steam stops.
How long does an overheated engine take to cool down?
At least 30 minutes, often longer on a hot day. Wait until the hood feels cool before you open the coolant tank cap. Never open the radiator cap on a warm engine.
Should I call a tow or a mobile mechanic for an overheating car?
If the car is parked somewhere safe, a mobile mechanic can often fix a hose, the thermostat or the fan on site. If it is leaking a lot or smoking, a tow is safer.