An overheating engine can usually be narrowed down to 4 things: 1. radiator 2. fan 3. thermostat 4. heater core.

If it is not one of these four things, you have major engine problems.

When the car is cold, take the radiator cap off. Start the car. While the car is running, watch the water in the radiator. When it warms up, the thermostat should open, and the water should start circulating.

If the car seems to just heat up without pausing at normal temperature, you probably need to replace the thermostat. This is usually not a major operation, but you do need to be careful.

If the thermostat is good, but the water is not circulating, check the heater core. To do this you need to take the heater core hoses off and run water through it. Usually if water runs freely through it, it is good.

Still no circulation. It is probably the radiator. Take it out, have it fixed or replace it.

Fans are a different story. If you have an electric fan, just see if it turns on when the car warms up.

Fan clutches usually cause the engine to overheat at idle, or cause a vibration, when they go bad. If you are stuck in traffic, idling, when it overheats, it could be the fan clutch.

I am really only covering the things that most do-it-yourselfers can handle. The fifth thing is the water pump. This is usually not a job for a home mechanic. If the water pump is leaking, it is bad. It can also cause a vibration. On older cars I used to recommend replacing the water pump at about 75,000 miles. If I was replacing a timing chain, I would usually recommend a water pump also. Newer models are a little different.

Another thing I forgot to mention: Check the water!

Learn more about this author, Ross Valigura.
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