Why is My Car Overheating: 3 Reasons You Have Cooling Problems

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You've spent time working on getting your vehicle on the road but you've run into one big problem; your car is overheating. Whether it's happening while driving or stopped at light, you're literally in "hot water" when it comes to keeping your engine cool.

There are some simple factors that may affect your cooling ability that should be checked and ruled out before diving deeper into diagnosing your radiator and cooling system. Here are the 4 most common "quick fix" issues that need to be ruled out first:

  • Low Coolant Level
  • Fans not working properly
  • Stuck Thermastat
  • Clogged Radiator

If you have ruled out these 4 item as contributing to your cooling issues, then a deeper evaluation of your cooling system is needed.

(In this case, we are assuming that your radiator is in the stock location and is the stock/OEM construction, with the engine sitting behind the radiator, and that the vehicle has been modified and now produced more horsepower than the original OEM vehicle.)



1. Radiator Capacity

You've built up or modified your vehicle to squeeze some more horsepower out of your vehicle, but are constantly overheating when moving down the road, even at high speeds. This is the first indication that your radiator doesn't have the physical capacity to dissipate the heat being produced by your engine. The issue can be broken down into two factors:


Radiator Size

Often, the case is that you have a radiator that is not large enough for the heat load that your engine is generating. This can be corrected by creating a radiator that has a larger, denser,more efficient core. Essentially, this is done by adding cubic inches of core; either through making a thicker radiator or increases the radiators core dimensions by length and width. All of this can be achieved with a properly built, high quality, performance radiator.

Note: Equally as important as the cubic inches of core in your radiator, is the efficiency and design of the fins and tubes within in that area. To learn more about radiator core design, please see our article Radiator Cores- Tubes and Fins Explained


Coolant Volume

A radiators' ability to dissipate heat is directly related to the amount of coolant in the in the radiator, and the surface area the coolant is exposed to in the tubes. There is a certain minimum amount of overall coolant volume that your system needs to hold. A huge heat transfer gain can be made by locating as much coolant as possible to the core of the radiator. By placing as much coolant as possible into the tubes you will ensure that the coolant is doing as much as it can to contribute to your cooling system.

Note: The type of coolant you use also make a difference. Most systems will work just fine with a standard 50/50 mix. For high performance application, or for an addition edge, consider one of the waterless performance coolants from Evans Cooling.



2. Air Flow / Air Resistance

Your radiator may have the proper capacity for your engine or horsepower but without proper air flow over the core to dissipate the heat, your radiator will not be able to transfer heat and will not cool properly. This could be a cause of your car overheating, if you tend to be overheat at idle and/or at low speeds, but run cool at highway speeds.

The 2 most common issues when it comes to air flow or air resistance in a cooling package are:


Air Flow Restriction

This happens when there are factors restricting the flow of air. It can be caused by several factors, the most common are:

  • Air Conditioning Condenser (which will not only add restriction, but preheat the air temperature 15-20 degrees before it hits the radiator)
  • A New Performance Radiator (with more cubic inches of core, generally thicker than OEM)
  • Intercooler or Transmission Cooler (sitting in front of the radiator, blocking some air flow)
  • Radiator Location, relative to the airflow


Insufficient Air Flow

Fans and shrouds are an important part of the cooling system and need to be matched to the application carefully. The best radiator in the world will not perform if it doesn't have the proper air flow through the core. Also, fans should cover as much surface area of the core as possible and this is why shrouding (engine side) is so important. A shroud allows the "puller" fans to pull air across the whole surface of the core; rather than un-shrouded fan(s) which will only pull air through the core directly in front of the fan(s).

Note: In some cases fans may be put on the grill side of the radiator due to space issues. NO SHROUDING should ever be used with grill side fan (pusher style) as it will create an obstruction as mentioned above.

Any of these can cause a scenario where there is insufficient airflow. the solution in this case would be to consider a shroud for your mechanical fan and/ or a full upgrade to an electric fan package.



3. Coolant Flow Rate

There are 2 scenarios here to look for:

  • Too Fast: Coolant is "pumping" and flowing through your radiator too fast and the coolant doesn't spend enough time in the radiator tubes to dissipate heat and cool down properly. This issue is most often caused by modern "high volume" water pumps. Is not likely with an all aluminum radiator with the large tubes , but it can happen. The obviously solution here be to decrease the flow rate, either with a slower pump or by restricting the flow.
  • Too Slow: It is also possibly that your engine temperature gauge show you are running to hot, yet your radiator is working perfectly. In this scenario the coolant going out of the radiator is sufficiently cooled but the coolant if staying in the block for too long. In this case the solution would be to increase the flow rate thru the system

Still confused on why you keep overheating? Contact our specialist today and we'll help diagnose the problem and provide some solutions! (716-655-6760)

What other factors do you feel contribute to engines overheating or general cooling problem? Let us know by contacting us via email, sales@wizardcooling.com

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