Car Overheating

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Reader Question:

Hey there Austin! My car engine is giving me some issues (again) because it is overheating. What causes my car to overheat?
Thanks in advance, Ruth

Good morning Ruth!

Overheating questions are some of the most frequent emails I receive, and the first thing we need to do is to pinpoint the source of the overheating symptoms.

Step One:

Check the antifreeze/coolant level in your radiator. When the engine is cold, remove the radiator cap and do a visual inspection. If the car has enough coolant fluid, you should be able to see it. If you can add more than one pint of fluid, you need to rule out a leak by having a cooling system pressure test. Also have this test performed if you notice any signs of fluid loss under the hood or on the ground.

Step Two:

If the car doesn’t have low fluid and/or signs of a coolant leak, you need to determine when the car is overheating.

Is the car overheating when it is idling or at a stop?

Directly behind or in front of the radiator of most front-wheel-drive cars is an electric fan. This cooling fan is designed to keep the radiator cool by providing airflow across the radiator when the car is traveling at low speeds and at stops. It has sensors that control the fan and are responsible for regulating the engine temperature. If this fan is not working as it should, the car can overheat.

To check the cooling fan in most cars, turn on the air conditioner. If the cooling fan is operating properly, it should come on when the air conditioner compressor comes on. The exception to this test scenario is if your car has two electric fans. If that is the case with your car, the one closer to the middle of the radiator will be the radiator fan and the other is the air conditioner condenser fan. The radiator fan cools the engine and the condenser fan increases the efficiency of the air conditioning system when the car is at idle and low speeds. In cars with two fans, the radiator fan will only come on when the engine temperature heats up.

If you don’t see an electric fan at all, you car will be equipped with a belt-driven fan along with a fan clutch. This type of fan is also designed to pull large quantities of air across the radiator.

No matter what kind of fan your car uses, you need to determine whether or not your car is getting enough air flow across the radiator when the car is idling. Adequate air flow is critical because the radiator is the main heat exchange mechanism for the engine.

Is the car overheating on the freeway or at high speeds?

Unless there is an obvious blockage of the front grill of the car, you should be getting adequate air flow across the radiator at high speeds. So if the car overheats at 55 MPH, you need to verify that the car is getting good coolant/antifreeze circulation.

The water pump is the heart of the car and is responsible for pumping the hot antifreeze through the cooling system. Any restriction or blockage in the system will decrease circulation and can cause overheating problems. Common causes are a restricted radiator, a kinked radiator hose, and a stuck thermostat.

Radiator restrictions are usually created by water calcification and rust accumulating in the radiator. These problems can significantly reduce coolant flow, especially at high speeds. Correcting a clogged radiator problem requires removal of the radiator, dis-assembly, and proper cleaning. In severe cases, the radiator may require replacement.

There are radiator flush products on the market that can be used as an additive for preventative maintenance; however, once the radiator condition is bad enough to restrict coolant flow, it’s not going to do the trick. I have written an article on radiator flushing that you can access through the archive link below if you want to check it out.

Hopefully going through these action items will help you to identify the origin of your overheating problem. If you are unable to locate the source of your problem as one of these issues, it is possible that you have a more technical problem and will need to see a mechanic.

Remember, performing this initial investigation yourself and reporting your findings to the mechanic can help him to diagnose the problem more efficiently, and will hopefully save you time and money in the diagnostic stage of the repair.

I talk about other problems like this in my eBook What Your Mechanic Doesn’t Want You to Know

Austin Davis

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Posted in: Over Heating

About the Author:

Austin Davis, consumer car repair advocate. "Hi there! I love to help people solve their car repair problems and I hope my site was helpful to you today. Thank you for stopping by."

6 Comments on "Car Overheating"

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  1. I would look at the radiator and make sure there is not a restriction at the bottom, and time to replace it. Lack of air flow across the radiator and lack of coolant circulation in the radiator are usually what causes overheating under a load, like climbing a hill or pulling a trailer.

  2. solomon kingz says:

    My car rover 75 overheat all the time. Why?
    It does not move fast when climbing the hill also.

  3. At the front of the car is the radiator, and the two radiator hoses coming off it going to the engine. Then at the very front of the engine just behind the fan belt is the water pump. can you see any sign of coolant leaking at those locations under the hood?

    If you can not, then I would have your local mechanic do a “cooling system pressure test” to help you locate the leak. This is a simple, fast and inexpensive test that pumps air into the radiator to help push out the coolant so you can find the source of the leak.

  4. Lele says:

    My antifreeze keeps leaking out. It seems to be coming out toward the front end of the car. The reservoir rarely stays full it like the car s drinking the fluids quickly. It overheats when its empty…what could be the problem?

  5. Hi there, I dont quite understand your question. The floor of the car is hot, but not the engine? No overheating is happening under the hood?

  6. kencool says:

    My car heating indicator was at half. I put my laptop to the floor at the back seats but it was very hot by the time I arrived home. could this be the overheating I hear about?

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