If you drive a motor vehicle, you depend on several off line cooling system parts working flawlessly to keep your engine at a constant temperature, whether it’s 110 degrees outside or 10 below zero. The process sounds simple: heat from the engine is transferred to liquid coolant, the coolant moves to a radiator to lose some of its heat to air, and then the cooled liquid returns to the engine.

The capacity of a cooling system is designed to match the size and power of a specific engine. The larger V8 engines of heavy vehicles require more capacity than the 4-cylinder engines found in small cars. The larger engines generate more heat, too, because they have many more spark plugs igniting the fuel in each cylinder to produce the explosions that propel your car down the road.

These hot sparks produce a tremendous amount of heat, and if left uncontrolled, could destroy your engine within minutes. The cooling system must transfer that heat to the air outside the engine to keep it at a safe operating temperature.

During normal operation, the cooling system transfers heat to the air by drawing in outside air through a large radiator. The radiator is surrounded by electric fans that blow the air over the fins to increase the surface area and help the coolant move faster through the radiator. This is called forced air cooling.

While the force of the air flowing over the cooling fins creates some evaporative cooling, the most important part of a cooling system is its thermal insulation, which reduces the flow of heat between the radiator and the engine block. This helps prevent the temperature of the engine from rising too rapidly, which can lead to overheating.

A second kind of cooling system, referred to as an indirect-flow or closed-loop cooling system, uses the ambient air to cool the engine by passing it through the radiator and forcing it out through the hood or cowling. This allows the engine to use less water for cooling, which increases its efficiency and saves energy.

Some cooling systems use an evaporative pad to remove heat from the air by absorbing moisture in the form of droplets and releasing it back into the air as a cool mist. One gallon of evaporative water can remove as much as 8,000 BTUs of heat from the air. This type of cooling system also improves indoor air quality by minimizing mildew and allergens.

Another cooling technology, called a forced-air oil cooler, is used to cool hydraulic fluid in industrial or agricultural equipment. These units are commonly installed on tractor hydraulic systems and are referred to as heat exchangers. Heated hydraulic oil can cause excess wear on seals and surfaces, and they must be kept cool to extend the life of the equipment. Oil coolers work by cooling the hydraulic oil by circulating it through internal turbulated tubes that are similar to O2A tubes, and they can be made from stainless steel or aluminum.