Foundations for a Functioning Cooling System -
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Foundations for a Functioning Cooling System

Adapted from Counterman


The radiator is one component no car or truck can run long without. The radiator’s job is to cool the coolant that circulates through the engine so it doesn’t overheat. Consequently, if the radiator leaks, the coolant will soon be lost and the engine will overheat.


Looking into Leaks
Leaks can be caused by internal corrosion (not changing the coolant often enough), vibration (that causes hairline cracks typically at hose connections) or by external punctures (due to road hazards or collision damage). Other causes of radiator failure include freezing damage (not having the correct ratio of antifreeze in the water/coolant mixture) and steam erosion of plastic end tanks (usually due to a low coolant level and/or overheating).

If a radiator is leaking, it must be repaired or replaced to stop the loss of coolant. Even a tiny leak that seeps only a few drops a day will eventually allow enough coolant loss to make the engine run dangerously hot. The capacity of many cooling systems today is only a couple of gallons, so any loss of coolant greatly increases the risk of overheating, boilover and possible engine damage.


A cooling system sealer can be added to a leaky radiator to temporarily seal a leak. There are also special epoxy glues that can be used to patch leaks in aluminum radiators. But the only permanent fix for a leak is to have the radiator professionally repaired by a radiator shop, or to replace it with a new one.

New radiators cost about the same as repaired radiators, and many customers don’t want to wait for a shop to patch their old radiator. What’s more, replacing an old leaky radiator with a new one eliminates any worries about internal corrosion causing the leak to return. Most new radiators also come with a better warranty than most radiator shops offer on repaired ones.


Did You Know…
Radiators on most late-model vehicles are aluminum with either aluminum or plastic end tanks. Most radiators on older vehicles have a copper/brass core with metal end tanks. Aluminum’s advantages are its lighter weight and resistance to corrosion because it has no lead-soldered joints. Though it isn’t essential to use the same type of replacement radiator, aluminum radiators should generally be replaced with the same to maintain the same cooling characteristics and corrosion resistance.

Attention to Application
To consolidate applications, many replacement radiators are designed to fit a wider variety of applications than an OEM radiator. As a result, the height, width and thickness of the replacement radiator and the locations of the hose connections may differ slightly from the original. But as long as the unit fits the radiator opening, the hoses line up and it cools the same or better than the original, it should work fine.


On some applications, it may be a good idea to install a larger or more efficient radiator (one that has a thicker core and/or more fins per square inch) to improve cooling capacity. Engines that are used for towing or racing generate more heat and need increased cooling.

For high-performance applications, a fin count of 12 to 16 fins per inch is often required. Serpentine-style radiators are sometimes used to improve cooling because they can be manufactured with more fins per inch. Louvered fins can also improve heat transfer for better cooling.

To cool efficiently, the radiator must be clean, in good condition and receive adequate airflow. The radiator’s front-mounted location ensures good airflow when the vehicle is in motion, but at speeds below 25 to 30 mph, additional airflow must be provided by the fan. If an engine has been overheating, the fan should be checked to make sure it is operating correctly.


On newer vehicles with electric cooling fans, a faulty temperature switch, fan relay, fan controller or fan motor may prevent the fan from coming on. On older vehicles with a mechanical fan, a slipping fan clutch or belt may be turning the fan too slowly to provide adequate cooling. Most fan clutches have a service life that is about the same as the water pump, and should be replaced when the water pump is replaced.

If a customer is buying a new radiator, he or she should be advised to clean and flush the cooling system. Simply draining the old radiator can leave up to 60 percent of the old coolant in the engine. To remove all of the old dirty coolant, the system needs to be flushed with clean water or with equipment that exchanges new coolant for the old.


Did You Know…
Softened water or tap water should never be used to refill a cooling system because softened water contains chloride (which is very corrosive to aluminum), and tap water contains dissolved minerals (which can form lime deposits). Recommend distilled water only mixed with equal parts of antifreeze.

Topping Off
A 50/50 mixture of distilled water and antifreeze will provide the proper freezing, boilover and corrosion protection. The type of antifreeze should be that recommended by the vehicle manufacturer, or a “universal” antifreeze that meets OEM specifications.

Other items that should also be replaced when changing a radiator include the radiator cap (make sure the pressure rating is the same as the original), radiator hoses (upper and lower), heater hoses and hose clamps.


The cap’s job is an important one because it keeps the cooling system pressurized. This not only prevents the loss of coolant, but also raises the temperature at which the coolant boils. A 15 psi cap will raise the boiling point of a 50/50 coolant mixture more than 30 degrees, which can provide a lot of additional boilover protection during hot-weather driving.

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