Welcome to zhongcai!


Email: gdzcee@gmail.com

Three minutes let you know how engine cooling system working

Nov 12, 2021

Engine cooling system is the important system which can maintain normal temperature of engine and ensure it normal working. It’s structure is not complicated, and few fault spot. Today we would like to talk a little about it.

The function of cooling system that keep the engine maintain suitable temperature range under all operating conditions, not only avoid engine overheat, but also avoid engine undercooling in winter. After the engine cold starts, the cooling system also ensures that the engine heats up quickly and reaches the normal operating temperature as soon as possible.

The harm of engine overheat

(1) Reduce the efficiency of air inflate, power down the engine.

(2) The tendency of deflagration is increased, which causes early damage to parts due to additional impact load.

(3) The normal clearance of moving parts is destroyed, the movement blocks, the wear increases, even damages

(4) The deterioration of lubrication aggravates the friction and wear of the parts.

(5) Mechanical degradation of parts, resulting in deformation or damage.

The harm of engine overcool

The temperature of the mixture (or air) into the cylinder is too low, the quality of the combustible mixture is poor, making ignition difficult or slow combustion, resulting in engine power decline, fuel consumption increase;

Water vapor in combustion products is easy to condense into water and form acids with acidic gas, which aggravates the erosion of the body and parts

The oil film on the surface of the parts (cylinder wall, piston, piston ring, etc.) is diluted by the non-vaporized fuel washing, which makes the parts wear more.

The cooling mode of engine

According to the different cooling medium, there are two ways of cooling the engine: air-cooled and water-cooled.

Nowadays most of engine are water cooled, the air-cooled is only used in some special vehicles, some engineering machinery and motorbikes. So today we would only talk about water-cooled systems.

The water cooled system of vehicle engine is forced circulation water cooling system, that is use water pumps to increase the coolant pressure, forced coolant in the engine circulation flow. This system including of water pump, radiator, cooling fan, thermostat,compensation reservoir, engine body, water jacket in cylinder head and other additional device etc.

How to working of cooling system of engine

The system circulating water cooling is use water pumps to pressurize coolant of system and make it flow in water jacked. Cooling water absorb heat from air cylinder, when temperature increased, the hot water flows up into cylinder head, and then flow out from cylinder head and into radiator. Because of strong suction action of fan, the air flow through radiator at high speed from frond to back, and continually take the heat away from the water flowing through the radiator.

The cooled water is pumped back into water jacked from the bottom of radiator, water continually circulating in cooling system. For control the temperature of cooled water, the system equipped with cooling intensity regulation device, like the window shades,thermostat and fan clutch etc.


The radiator is what we often say cistern, including types of vertical flow and horizontal flow. Most of new car use horizontal flow of radiator, This can make the outer profile of the hood lower, which is conducive to improving the aerodynamic performance of the front end of the body.

Steam valve is generally in the radiator pressure reached 126kPa~137kPa, valve open, part of the steam into the atmosphere through the deflator, to avoid damage to the radiator

Air valve in the radiator air pressure down to 99kPa~87kPa, air valve open, the radiator and the atmosphere, prevent the radiator core by atmospheric pressure damaged.

expansion tank

Expansion tank multi-purpose translucent material (such as plastic) made. The upper part of the expansion tank is connected to the feed pipe of the tank with a thin hose, and the bottom is connected to the inlet side of the pump through the pipe, usually slightly above the radiator.

The cooling system is changed into a permanent closed system to prevent air from entering, so that the water and steam in the cooling system can be separated, and the pressure in the system can be kept stable.

Supplementary coolant: there are two lines on the expansion tank. The coolant should be added to the upper line (FULL). When the liquid level drops to the lower line (LOW), it should be replenished in time.

Water pump 

The use of water pump is pressure the coolant to ensure it circulating flow in the cooling system. the centrifugal water pump are widely used on automobile engine now.


The function of the fan is when the fan is rotating to suck in the air and make it through the radiator, in order to enhance the radiator heat dissipation capacity, speed up the cooling speed of the coolant. 

Most of cooling system of car engine use electric fan so that is irrelevant to fan rotate speed and engine rotate speed. In some of electric control system, electric fan is controlled by computer. When engine stop, the electric fan still rotating a few minutes due to the high water temperature so that cooling the engine more convenience.

In the frond of say, if you want to ensure engine working in best temperature and not appear the status for overcool or overheat, that must be able to auto adjusting the cooling strong system of engine according to change of using condition .

Adjusting cooling system way: one is change the flow of air through the radiator and flow speed; two is change the coolant flow and circulation route.


The role of the thermostat: with the engine load and the size of the water temperature and automatically change the coolant flow and circulation route, to ensure that the engine in the appropriate temperature to work, reduce fuel consumption and wear parts.

The large circulation of water cooling system

The cooling water is through by water pump-water jacked-thermostat-radiator, and then through water pump press in circulation of water jacked, the water flow route is long, the heat dissipation intensity is large, so called large circulation of water cooling system.

The small circulation of water cooling system

The cooling water after through by water pump-water jacked-thermostat and then press in cycle of water jecked directly, no need through radiator. The water flow route is long, and heat dissipation intensity is small. So called small circulation of water cooling system.


That is all,  do you understand?