How to Diagnose an Overheating Car

by Louise Balle
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yellow car, a honda japanese sport car model image by alma_sacra from

An overheated car is a problem that has to be taken care of right away. If you don't take care of this issue, the car will eventually shut down and you could have additional problems. So it's best to diagnose an overheating issue as soon as possible and get it fixed. When your car is overheating, there are some fairly obvious symptoms to look for that will tell you it's time to bring it in for servicing.

Step 1

Check the temperature gauge on your dashboard, if your vehicle has one. If it's well over the midpoint between cold and hot, that's your first clue that your car is overheating.

Step 2

Check for smoke coming from under the hood. A smoking engine is a clear sign that it's way too hot.

Step 3

Open your car's heating vents. If the heat coming into the car is hotter and more intense than usual, the engine could be over its usual temperature level.

Step 4

Listen for an unusual knocking or bumping sound under the hood, which could be a symptom of an overheated engine.

Step 5

Check your anti-freeze level. If it's very low even though you've just recently filled it up, that could be a reason why the car engine is overheating. It could also be an indication that there's a coolant leak somewhere. As the name indicates, the engine uses coolant to cool itself off--if for some reason coolant isn't getting through the system, that will cause the car's temperature to rise.

Step 6

Lift up your car's hood and turn on the motor. Get back out and listen to your car. If you don't hear or see the radiator fan whirring, that will cause your car to overheat. The fan helps keep your engine cool when you're driving slowly and idling.

Step 7

Check your car's thermostat. A quick way to do so is to open the hood, remove the radiator cap and start your vehicle. If you don't see a sudden drop in the level of coolant in the holder as the car warms up, there's a chance that the thermostat is stuck closed, which can be a cause of an overheating car. Make sure you engage your car's parking brake when you do this test, just in case.

Step 8

Check the front radiator hose (commonly located right at the front of the car above the radiator). If you see coolant leaking, this will cause your car to overheat since the engine is not getting sufficient fluids to cool itself off. Open up the radiator cap and check inside to see if there is any fluid inside--if not, that's a problem.Check the cylinder head gasket as well to see if coolant is leaking from that area--this is a seal located between the coolant tank and the combustion chamber (see "Resources" for a picture). If the gasket is bad, it will cause an overheating problem.

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