Stop an Engine from Overheating
If your car's cooling system is not working properly, heat can destroy your car's engine. If you notice your car starting to overheat, taking the following steps can help prevent harm to your vehicle until you can repair your cooling system.
What to Do If It's Safe to Stop the Car
- Pull over. As soon as you notice the temperature gauge creeping into the "H" territory (which stands for "hot"), pull over and turn off your car to allow the engine to cool. Be extra aware of the temperature gauge on hot days.
- If you start to see steam emanating from your hood, stop immediately. You may be able to prevent serious steam from escaping in the first place by keeping an eye on your temperature gauge.
- Open the hood to allow heat to disperse faster. Don't keep all that heat trapped up there. Find the little latch underneath the hood and open the hood. Be aware that some cars have safety latches close to radiator cap and there is a risk of getting burned if steam is coming from radiator cap.
- Do not open your radiator pressure cap (the cap on top of the radiator) while the engine is hot. Doing so is very likely to release a high pressure combination of steam and radiator fluid that can cause very serious burns.
- Check the coolant reservoir tank and fill if needed. Most modern cars have a plastic reservoir of coolant connected to the top of the radiator. This will allow you to see if your coolant is low. Many have marks indicating the proper level of coolant, below which the engine is in danger of becoming too hot. Check to see if the coolant is at or below that level.
- Add coolant (or water, in a pinch) to your reservoir to the full/hot line. On most cars, you can add liquid to your reservoir even if the car is hot. Check the owner's manual to be sure, or wait for the car to cool before opening.
- If your car only has a radiator and no coolant reservoir, you must wait for it to cool before checking the level of coolant.
- Look for a leak in the cooling system. If your radiator or cylinder head seem to be compromised, or if you open the coolant reservoir and the levels are topped up, you may have a leak in the cooling system. If you're experienced with cars, check the radiator, core plugs in the engine block, or cylinder head near the head gasket for any signs of leakage.
- If you don't know your way around cars, consider bringing your car to the nearest mechanic and ask them to pressure-test the cooling system. Pressure-testing the cooling system is relatively easy to do; they may even do it free of charge.
- Determine whether to drive on or call for help. If the car was simply low on coolant and you were able to refill it, it may be safe to drive on. Follow the instructions below for how to minimize the risk of overheating if you do so.
- If the car appears to be out of coolant entirely, do not drive it. You can quickly cause severe harm to your engine by doing so.
- If help is readily available, you may be better off calling for a tow truck than driving the car.
- If no help is available or conditions are otherwise unsafe you may need to drive on regardless of whether you were able to solve the problems. Read below for how to manage your car if this is the case.
What to Do If You Must Drive the Car
- Turn the air conditioning off. If your car has air conditioning, turn it off. Air-conditioning puts a load on the engine that you want to avoid right now.
- Use the heater to disperse engine heat. It may sound crazy, but it actually works. Flip the climate controls to vent, turn the heater all the way up, and turn the fan all the way up. If the weather is hot, the inside of the car will heat up quite a lot. Point the vents out the windows as much as possible to help reduce the temperature.
- Why this works: The heater in your car uses engine heat to warm air in the cabin. Running your heater full blast takes a significant amount of heat away from the engine, making it significantly cooler.
- Keep a close eye on the temperature gauge or light. Pull over and turn off the engine if you have to. Remember that if your car overheats too much, it will ruin the engine.
- Turn off your engine (under certain circumstances), but flip your key back into "ignition" as soon as it stops. The engine will shut down, but both the radiator fan and blower will keep cooling down coolant. Do this only if you are sitting in traffic or stopped at a light and not moving for more than a minute. Keep a lookout ahead for when the traffic will move and turn your engine on before that point.
- Keep it steady in stop-and-go traffic. It is better to move at a steady slow pace than to go fast, stop, go fast stop, etc. Accelerating quickly and then riding the brake will increase the load put on the engine, causing it to work overtime.
- Generally, people will not cut you off in stop and go traffic since everyone is stuck in the same situation. Either way, you probably want to be more worried about your engine overheating than someone getting in ahead of you.
- Wait out rush hour traffic. Pull over if you think your car will break down in stop and go traffic. Turn off the engine and wait for the traffic to start moving normally. Once the traffic starts flowing again, it is better for you to drive faster than slower as more air will come in and cool your engine.
- If your coolant is leaking, you will have to continually replenish it. Pull into locations likely to have a water source that they won't mind you using. Many service stations have water you can use.
- Take your car to a mechanic ASAP. While the above steps are good when you're in a pinch, they won't help in the long run.
- Coolant filler pressure caps are failing by the thousands after eight years of service costing thousands of dollars to be spent for unneeded repairs that don't help. If your vehicle is eight years or older, replace the cap before trouble starts! A vehicle that looses coolant when the engine is turned off very likely has a cap that is not holding the required pressure (most require 15 or 16 lbs).
- If your car has electric radiator fans, you may be able to activate the electric fans with the engine off. With the car overheated, turn the ignition off (to stop the engine) and then back on without starting the engine. On some cars, the electric fans are wired to turn on even with the engine off.
- If you have lost water pump belt, or water pump has failed internally you will be unable to continue driving without overheating even at cold weather, because coolant will boil at hot spots inside engine creating vapor that further promotes overheating.
- When possible use a proper water/antifreeze mixture in your vehicle's cooling system. Water should only be used in emergencies, and after the cooling system problem solved have the system completely drained and refilled with the proper antifreeze water mixture.
- In extreme cases, the engine may continue running after you turn the key to off. This is because the engine is so hot that it is auto-igniting even without the electric spark. In this situation put on the handbrake and then put the car into gear. This should cause the engine to stall.
- If your engine is overheating due to excessive load (such as driving up a long, steep incline or pulling a heavy trailer) it is typically better to pull off to the side of the road, open the hood and wait.
- If you are in slow-moving traffic, you can pop your hood. It will stay closed on the safety catch, but open a small gap, allowing greater ventilation (you'll see cops and cab drivers do this in big cities on hot days). Be aware that going at higher speeds and hitting a bump may cause safety latch to fail and the hood may open, smashing into windshield.
- To avoid the risk of very serious burns, do not remove a radiator cap from an overheated engine. Wait for it to cool.
- When filling your overheating car with water, never use cold water. When the cold water contacts the extremely hot engine, there's enough thermal stress to crack your engine block. Always allow the water to warm to ambient temperature.
- Regularly overheating a car can result in head gasket failure (causes blue smoke from the exhaust) which is very expensive to repair.
- Move a Radiator
- Change a Tire
- Fix Your Car's Air Conditioner
- Fix a Car That Stalls
- Open the Hood of a Vehicle
Sources and Citations
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- Change an Automotive Belt
- Cook Food on Your Car's Engine
- Drain the Gas Tank of Your Car
- Remedy an Overheated Engine
- Understand Compression and Power Systems in Small Engines