Cool an Overheated Engine

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Knowing how to cool an overheated engine is an important skill for any licensed driver. Being able to diagnose and fix your own issues can get you back on the road quickly, prevent costly mechanical issues, and help you learn when to seek professional help.

Handling an Overheating Engine

  1. Avoid panicking and pull over as soon as you can.An overheating engine, while serious, will not cause you immediate harm. If your temperature gauge hits the red or you notice steam coming from your engine, slow down and pull over as soon as you find somewhere safe. If you notice white clouds coming from your engine, it is not smoke but steam that is coming off an overheated engine, and you have some time to pull over. If you cannot immediately pull over, you should:
    • Turn off the AC and open the windows.
    • Crank the heat and fans all the way up–this draws heat from your engine.
    • Turn on your hazards and drive at a slow, constant pace until you can stop.
  2. Pop the hood when there is no more steam coming out.If the car isn’t too hot, turn off the vehicle and pop your hood. If the hood is extremely hot to the touch or if you see steam, then it is advisable to wait until the hood cools before you open it all the way. Opening the hood helps dissipate some of the heat away from the engine.
    • Turn the engine off and leave the key in the ignition in the “on” position. Your lights, dashboard, etc., should still be on. This will allow the cooling fans to continue running without running your engine, which will help speed the cooling process.
    • Let the engine cool completely before you touch the engine or open the radiator cap. This cooling process could take as long as 30-45 minutes, but will save you from dangerous burns.
  3. Check the upper radiator hose.Squeezing the upper radiator hose can help you determine whether your system is under pressure, and thus whether it’s safe to remove the radiator cap. If it feels firm and is difficult to squeeze, then the system is likely still pressurized and you should not remove the radiator cap. If the hose compresses easily when you squeeze it, it is probably safe to remove the radiator cap.
    • Use a rag or towel when you handle this hose, as it can be very hot.
  4. Leave the radiator cap on until it is cool.The pressure and steam inside can shoot a dangerous jet of fluid back at your face. Play it safe and leave the radiator cap on the car for as long as you can. If it feels warm to the touch, leave it.
    • An overheated engine may have coolant as hot as 260F. Inside a sealed system, it will not boil. However, once exposed to the air it will flash boil and can cause severe burns. Wait until the system is cool.
  5. Turn the radiator cap. Use a thick towel or rag to turn the cap carefully. The cap will expose the fluid inside the radiator or expansion tank to the atmosphere. If your radiator cap doesn’t have threads, you will need to push down on it after you’ve loosened it in order to clear the safety lock. This will allow you to remove the cap completely.
  6. Check your coolant reservoir tank once the engine has cooled enough. This usually takes 30-45 minutes. The reservoir tank resembles a white, plastic milk jug and is connected to the radiator cap. There is usually a mark on the side that lets you know how full it should be.
  7. Check the engine for leaks.The most common cause of engine overheating is a leak in the coolant system. Look for fluid on the engine or pooling underneath the car, especially if the coolant is low or empty. That said, cooling systems need pressure to function, so even a small leak that hasn’t drained a lot of coolant can cause problems.
    • Coolant usually smells sweet, and can show up on hoses, under the car, or around the radiator cap. It flows more like water, unlike oil which has a thicker consistency.
    • Coolant is often green for older models, but the color of coolant can vary depending on your car’s make and model.
  8. Refill the coolant after the car has cooled off.If you have coolant, add some to the car once it has cooled down, usually after 30-45 minutes. Open the radiator cap and pour a little in, 3-5 seconds worth. If you have water, mix the coolant and water together in roughly even parts and add that — most engines are made to function with a 50/50 mixture of coolant and water.
    • In a tight pinch, just water can substitute for coolant, though you don’t want to use it for too long.
  9. Turn the car back on after cooling and check the temperature gauge. Is it shooting back up into the red? If so, you should turn the car back off and wait another 10-15 minutes for it to cool off before driving. If not, you should be able to keep driving until you see a mechanic.
  10. Call a tow-truck if the issue doesn’t go away or you notice bigger problems.If you have a leak in the coolant system, are dripping oil, or can’t get the engine to cool down, call a tow-truck immediately. Engine overheating can completely ruin a motor, totaling your car if you aren’t careful.
    • If you must drive the car, be sure to let it cool as much as possible before restarting.

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