The purpose of engine cooling system

The purpose of engine cooling system is forced heat rejection from engine parts and transfers it to atmosphere. The result of these processes is creation optimal temperature of engine works and working cycle is proceeding normally. A vehicle engine produces a lot of heat when it is working, and it must be cooled continuously to avoid engine damage.

Why is it important to cool engine?

These systems take 25-35% of heat when engine is running and fuel-air mixture burning. The optimal temperature of engine works must be between 80-95°C. This mode provides normal engine working and it mustn`t the change from ambient temperature changing or engine loading.

Temperature can change between 80-120°C (minimum) in start inlet stoke  to 2000-2200 °C (maximum) in the end of power stroke. Engine parts are heat and expand if the engine is not cooling. Finally the oil begins to burns and so friction is up, and the parts expanding are led to pistons jammed in engine cylinder. That can be finish engine damage. To avoid the negative final of excessive engine heating, it must be cooling. 

Excessive engine cooling is not good too

However, the excessive engine cooling is not good for normal engine running too. Overcooling of engine leads to create condensate of fuel vapor on the engine cylinder walls. The condensate washes oil material and liquefy oil in the crankcase. These conditions create negative influence on the engine parts, e.g.  piston rings wearing, pistons and cylinders wearing. And engine power and efficiency is falling down.  

Normal engine cooling system functioning led to growing max power and engine efficiency, so fuel economy  and engine service life have increase too. The engine cooling system of forced heat rejection with close type is widespread. Open cooling systems are not use in vehicle.

Figure 1 is a schematic drawing of the engine cooling system.

Engine cooling system scheme

Engine cooling system construction: 1 – radiator; 2 – top tank; 3 – radiator cap; 4 – control tube; 5 – top radiator hose; 6, 19 –  rubber hoses; 7 – overflow hose; 8,18 – inlet and outlet pipes; 9 – thermostat; 10 – hole; 11 – cylinder block head; 12 – water distribution pipes; 13 – temperature sensor; 14 – engine cylinder block; 15, 21 – drain taps; 16 – motor cooling jacket; 17 – water pump; 20 – bottom radiator hose; 22 – bottom tank; 23 – fan drive belt; 24 – engine driven fan.

Engine cooling system construction

Engine cooling system consist of motor cooling jacket 16, radiator 1,fan 24, thermostat 9, water pump with impeller 17, inlet 8 and outlet 18 pipes, fan drive belt 23, temperature sensor 13, drain taps 15 and 21 and other parts. Around the cylinder of engine and head of cylinder is space with double walls (water cooling jacket and water cavity), where liquid circulations.

How an engine cooling system works

In time of engine working the cooling liquid heats up and water pump gives it to the radiator for cooling, than the liquid flows into engine water cooling jacket again. This circulation of cooling liquid (engine-radiator-engine) provides the reliable engine work.

Cooling liquid can circulation by small circle bypassing radiator (engine is not a hot and thermostat is close) or by a big circle through the radiator ( engine is hot and thermostat is open).