Car overheating on the road: what to do in the first 10 minutes

It is midday, the road is packed, and you are crawling along. Suddenly the temperature needle climbs past its usual spot. Not long after, a sweet smell comes from the hood, and now and then thin steam can be seen. In a situation like this, what you do in the first few minutes matters: the engine can be saved with simple steps, or be badly damaged because it is forced to keep running.

This article arranges the steps recommended by automotive organizations and manufacturer manuals into an order that is easy to remember, then explains the common causes of overheating and what needs to be checked afterwards. The goal is simple: you and your passengers stay safe, and the engine does not suffer damage that could actually be prevented.

An engine rarely overheats without signs. What is most often seen first:

• The temperature needle rises toward H (hot) or enters the red area. In normal conditions, the needle usually sits in the middle or slightly below.
• The temperature warning light or the check engine light comes on.
• A sweet smell from the engine area, which can come from leaking coolant.
• Steam that looks like smoke coming out from under the hood.
• The car feels slower and less responsive, or unusual engine sounds are heard.
• There is a puddle of coolant under the car.

If one of these signs appears, start the steps below without waiting for the condition to improve by itself.

If you cannot pull over immediately, for example stuck in a traffic jam, turn off the A/C to reduce the load on the engine. Then turn on the cabin heater and its fan. This step does feel uncomfortable, especially in hot weather, but the heater moves some of the heat from the engine to the cabin. Open the windows so the cabin stays bearable.

Remember, this is only a temporary step to reach a safe place. Do not continue a long trip with the heater on hoping the temperature will drop by itself.

As soon as there is a safe place, turn on the hazard lights, pull over away from the traffic flow, and turn off the engine. Some manufacturer manuals give slightly different intermediate steps: the Jeep Grand Cherokee manual asks the driver to pull over, turn off the A/C, move the transmission to neutral and let the engine idle, then turn off the engine if the temperature does not return to normal. Follow your car's manual if available.

If steam comes out of the engine bay, the Mercedes-Benz manual warns that steam from an overheated engine can cause serious burns just by opening the hood. Turn off the engine, get out of the car, and do not stand near the car until the engine has cooled down. Your passengers' safety and where you stand relative to traffic come first.

This is the mistake that most often leads to injury. The cooling system contains hot, pressurized fluid. If the radiator cap or the reservoir cap is opened while still hot, the fluid can spray out and injure the skin.

• Do not open the hood right away. Wait until the temperature needle drops to the normal position or the warning light goes out.
• Wait at least 15 minutes; one source recommends not touching the hood or the front of the car for about 20 minutes.
• If the cap must be opened, make sure the engine is completely cold and use a thick cloth to protect your hand.

After the engine is cool enough, open the hood and look at the coolant reservoir. Its level should be between the minimum and maximum marks. If it is low, add the coolant specified in the manual. In an emergency, clean water can be used temporarily so the car can reach a workshop, but the cooling system still needs to be checked and filled with the correct mixture.

Also watch for signs of leaks: drips under the car, hoses that are wet or cracked, and fluid traces around the radiator. Then start the engine carefully and watch the temperature needle. If the needle rises again, stop the car again and let it cool. Adding coolant is only an emergency step; the cause of the overheating still has to be found.

Do not continue the trip if the temperature immediately rises again after the engine is started, the coolant keeps dropping, there is thick steam, the engine sounds rough, or the oil pressure light also comes on. Continuing to drive with an overheated engine can damage the cylinder head gasket, or even make the engine seize. In this condition, it is safer to have the car towed to a workshop than to push on.

Besides the temperature needle, there are several signs that help confirm the engine really is too hot:

• A burning or sweet smell. When the engine is too hot, plastic and rubber components can start to melt and smell burnt, while burning coolant smells sweet. If the A/C or heater is on, this smell can be pulled into the cabin; open the windows to let the fumes out.
• Ticking or thumping sounds from the engine. These sounds can appear when coolant boils inside the engine, or when there is a lubrication problem.
• A very hot hood and power that feels reduced when accelerating.

Do not rely only on the temperature needle. If other signs appear even though the needle looks normal, still pull over and turn off the engine.

• Make a habit of checking the coolant level regularly and before long trips, when the engine is cold.
• Use the coolant and water mixture specified in the manual, and replace the coolant on the manufacturer's schedule.
• Fix any leak, however small, as soon as possible.
• Change the oil regularly, because low oil also makes the engine run hotter.
• Watch the temperature needle while driving, especially in traffic and hot weather.
• Carry spare coolant, drinking water, and a fully charged phone on long trips.

Low engine oil can also make the engine run hotter, because oil also carries heat from inside the engine. Check the oil level every time you check the coolant.