The Cooling System

4 Jun

Photo courtesy of

The several engine processes previously discussed are how the engine runs, but what keeps it running are almost separate entities entirely. The additional system I’ll be investigating is the cooling system.

What does the cooling system do other than the obvious? Essentially it is what keeps the engine from seizing; it keeps the parts moving and functional. This process happens I a few steps:

Internal combustion causes an immense amount of heat to be expelled on the surrounding machinery in an engine – this fact actually is beneficial because the engine coolant allows the most engine-efficiency when it’s around 200 F (93 C). Without the cooling system the engine easily approaches 4,500 F. While the coolant is necessary, it’s still more efficient for the engine to run “hot:” This allows the most efficient combustion of fuel (allows the air/fuel to vaporize in the cylinder), it increases oil viscosity allowing for the most effective lubrication of moving parts, and the metal parts wear less.

Cooling systems are either liquid or air based: Air cooling is more typical of older vehicles (old Volkswagon Bugs or buses). These function by having the engine block covered in aluminum fins that help circulate air from a fan through the engine and conducts heat away from the it. Liquid cooling systems, on the other hand, circulate a liquid coolant through a series of pipes through the engine block. The fluid absorbs heat put out by the engine and moves it through a series of paths. Nearly all current vehicles are liquid based cooling systems. Lets further investigate the pathways the coolant can take.


Photo courtesy of

The coolant fluid begins at the pump. Once the engine starts, the pump sends the liquid to the engine block via plumbing, and from the engine block it’s sent on a return path through the cylinder heads. At the exit of the engine block a thermostat is located: the thermostat is an open/shut valve. Once the engine has reached a certain temperature, the thermostat opens allowing fluid to be cycled through the radiator to be re-cooled and returned to the pump. Until the engine has attained that temperature however, the thermostat is in a closed position and the fluid is returned directly to the pump. On certain cars, the radiator has a built in cycle for cooling the transmission where oil is pumped into this portion of the radiator.

This simple overview of the cooling system is what keeps the engine functional: if the cooling system were to malfunction, the heat within the engine block could allow the pistons to become so hot that they weld themselves to the cylinder heads, among other potential issues. This is why cooling is so important, and why the radiator needs to be kept in good working order. 







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