The role of engine cooling system

The cooling system is designed to prevent the engine from both overheating and overheating. Overheating and undercooling will cause the normal clearance of the engine moving parts to be destroyed, the lubrication condition to deteriorate, accelerate the engine wear. Excessively high engine temperatures can cause coolant boiling, severely reducing heat transfer efficiency, premature combustion of the mixture, and possible engine knock, which can eventually damage engine components such as the cylinder head, valves and pistons. Engine temperature is too low, will lead to insufficient combustion, fuel consumption increases, engine service life is reduced.

Structural composition of engine cooling system

1. Radiator

Radiator is generally installed in the front of the vehicle, when the vehicle is running, the oncoming low temperature air constantly flows through the radiator, taking away the heat of the coolant, to ensure good heat dissipation effect.

The radiator is a heat exchanger that divides the high-temperature coolant flowing out of the cylinder head water jacket into many small streams to increase the cooling area and speed up its cooling.The coolant flows in the radiator core, and the air flows out from the radiator core. The high temperature coolant transfers heat with the low temperature air to achieve heat exchange. In order to obtain good heat dissipation effect, the radiator works with the cooling fan. After the coolant passes through the radiator, its temperature can be reduced by 10~15℃.

2, expansion water tank

The expansion tank is generally made of transparent plastic to facilitate observation of its internal coolant level. The main function of the expansion tank is to provide space for the coolant to expand and contract, as well as a centralized exhaust point for the cooling system, so it is installed in a slightly higher position than other coolant channels.

3. Cooling fan

Cooling fans are usually installed behind the radiator. When the cooling fan rotates, the air is sucked through the radiator to enhance the heat dissipation capacity of the radiator and accelerate the cooling speed of the coolant.

In the early stage of engine operation or low temperature, the electric cooling fan does not work. When the coolant temperature sensor detects that the coolant temperature exceeds a certain value, the ECM controls the operation of the fan motor.

Function and structure composition of engine cooling system

4, thermostat

The thermostat is a valve that controls the flow path of the coolant. It opens or closes the passage of the coolant to the radiator according to the temperature of the coolant. When the engine is cold started, the temperature of the coolant is low, and the thermostat will close the channel of the coolant flowing to the radiator. The coolant will flow directly back to the cylinder block and the cylinder head water jacket through the water pump, so that the coolant can quickly warm up. When the coolant temperature rises to a certain value, the thermostat will open the channel for the coolant to flow to the radiator, and the coolant will flow back to the pump after being cooled by the radiator.

The thermostat for most engines is located in the cylinder head outlet line. This arrangement has the advantage of simple structure. In some engines, the thermostat is installed at the water inlet of the pump. This design prevents the coolant temperature in the engine cylinder from falling sharply, thus reducing the change of stress in the engine and avoiding engine damage.

5, water pump

Automobile engine generally adopts centrifugal water pump, which has simple structure, small size, large displacement and reliable operation. The centrifugal water pump consists of a shell and impeller with coolant inlet and outlet channels. Blade axles are supported by one or more sealed bearings that do not require lubrication. The use of sealed bearings can prevent grease leakage and dirt and water entry. The pump shell is installed on the engine cylinder block, the pump impeller is fixed on the pump shaft, and the pump cavity is connected with the cylinder block water sleeve. The function of the pump is to pressurize the coolant and ensure that it circulates through the cooling system.

6. Warm air water tank

Most cars have a heating system that provides the heat source with engine coolant. The warm air system has a heater core, also called the warm air water tank, which is composed of water pipes and radiator pieces, and both ends are respectively connected to the cooling system outlet and inlet. The engine’s high-temperature coolant enters the warm air tank, heats the air passing through the warm air tank, and returns to the engine’s cooling system.

7. Coolant

The car will drive in different climates, usually requires the vehicle in the -40~40℃ temperature environment can work normally, so the engine coolant must have a low freezing point and a high boiling point.

The coolant is a mixture of soft water, antifreeze and a small amount of additives. Soft water does not contain (or contains a small amount of) soluble calcium and magnesium compounds, which can effectively prevent scaling and ensure cooling effect. Antifreeze can not only prevent the coolant from freezing in the cold season, avoid the radiator, cylinder block, cylinder head swelling crack, but also can appropriately improve the boiling point of the coolant, ensure the cooling effect. The most commonly used antifreeze is ethylene glycol, a colorless, transparent, slightly sweet, hygroscopic, viscous liquid that is soluble with water in any proportion. The coolant is also added with rust inhibitor, foam inhibitor, bactericidal fungicide, pH regulator, colorant and so on.