The engine cooling system in the car is designed to protect the working unit from overheating and thereby monitors the performance of the entire engine block. Cooling is an essential function in the operation of an internal combustion engine.
The consequences of an internal combustion engine malfunction can be fatal for the unit itself, up to the complete failure of the cylinder block. Damaged components may no longer be subject to restoration work, their maintainability will be zero. Care should be taken with responsibility and responsibility to periodically flush the engine cooling system.
By controlling the cooling system, the car owner directly takes care of the "heart health" of his iron "horse".
Purpose of the cooling system
The temperature in the cylinder block with the unit running can rise up to 1900 ℃. Of this volume of heat, only a fraction is useful and is used in the necessary operating modes. The rest is displayed by the cooling system outside the engine compartment. An increase in the temperature regime above the norm is fraught with negative consequences that lead to the burning of lubricants, violation of the technical clearances between certain parts, especially in the piston group, which will lead to a decrease in their service life. Overheating of the engine, as a result of a malfunction of the engine cooling system, is one of the reasons for the detonation of the combustible mixture supplied to the combustion chamber.
Engine subcooling is also undesirable. In a “cold” unit, a loss of power appears, the oil density increases, due to which the friction of non-lubricated nodes increases. The working combustible mixture partially condenses, thereby depriving the cylinder wall of the lubricant. However, the surface of the cylinder wall undergoes a corrosion process due to the formation of sulfur deposits.
The engine cooling system is designed to stabilize the thermal regime necessary for the normal functioning of the motor vehicle.
Types of cooling system
The engine cooling system is classified by the method of heat dissipation:
- closed liquid cooling;
- open air cooling;
- combined (hybrid) heat dissipation system.
Currently, air cooling in cars is extremely rare. Liquid can be of open type. In such systems, heat is removed through a steam pipe into the environment. The closed system is isolated from the outside atmosphere. Therefore, the pressure in this type of engine cooling system is much higher. At high pressure, the boiling threshold of the cooling element increases. The refrigerant temperature in a closed system can reach 120 ℃.
Air cooling
Natural supply air cooling is the easiest way to remove heat. Engines with this type of cooling emit heat into the environment using radiator fins located on the surface of the unit. Such a system has a huge lack of functionality. The fact is that this method directly depends on the small specific heat of the air. In addition, there are problems with the uniformity of heat removal from the motor.
Such nuances hinder the installation of both an efficient and compact installation. In the engine cooling system, air flows unevenly into all parts, and then the possibility of local overheating must be avoided. Following design features, fins for cooling are mounted in those places of the engine where air masses are least active, due to aerodynamic properties. Those parts of the motor that are most susceptible to heat are placed towards the air masses, while the cooler sections are placed behind.
Forced air cooling
Engines with this type of excess heat removal are equipped with a fan and cooling fins. This set of structural units allows you to artificially inject air into the engine cooling system to blow cooling fins. A protective cover is installed above the fan and fins, which participates in the direction of the air masses for cooling and prevents the ingress of heat from the outside.
The positive aspects in this type of cooling are the simplicity of design features, low weight, and the absence of refrigerant supply and circulation units. The disadvantages are the high noise level of the system and the bulkiness of the device. Also, in forced air cooling, the problem of local overheating of the unit and diffuse airflow has not been solved, despite the installed casings.
This type of prevention of engine overheating was actively used until the 70s. The operation of a forced air type engine cooling system was popular on small cars.
Liquid cooling
Liquid cooling system is by far the most popular and widespread. The heat removal process occurs with the help of liquid refrigerant circulating through the main elements of the engine through special closed highways. The hybrid system combines elements of air cooling simultaneously with liquid. The liquid is cooled in a radiator having fins and a fan with a casing. Also, such a radiator is cooled by the supply air masses when the vehicle is moving.
The liquid engine cooling system produces minimal noise during operation. This type collects heat everywhere and removes it from the engine with high efficiency.
According to the method of movement of liquid refrigerant systems are classified:
- forced circulation - the movement of fluid occurs using a pump, which is part of the engine and directly the cooling system;
- thermosiphon circulation - movement is carried out due to the difference in the density of the heated and cooled refrigerant;
- combined method - fluid circulation acts simultaneously in the first two ways.
Engine cooling system device
The liquid cooling design has the same structure and elements for both a gasoline engine and a diesel engine. The system consists of:
- radiator block;
- oil cooler;
- fan, with mounted casing;
- pumps (centrifugal pump);
- tank for expanding heated fluid and level control;
- refrigerant circulation thermostat.
When flushing the engine cooling system, all of these components (except the fan) are affected for more efficient further work.
Coolant circulates through the pipes inside the unit. The collection of such passages is called a “cooling jacket”. It covers the most exposed areas of the engine. The refrigerant, moving along it, absorbs heat and carries it to the radiator unit. Cooling down, he repeats the circle.
System operation
One of the main elements in the device of the engine cooling system is the radiator. Its task is to cool the refrigerant. It consists of a radiator crate, inside which tubes are laid for the movement of fluid. Coolant enters the radiator through the lower pipe and exits through the upper, which is mounted in the upper tank. On top of the tank there is a neck closed with a lid with a special valve. When the pressure in the engine cooling system increases, the valve opens and the fluid enters the expansion tank, which is mounted separately in the engine compartment.
There is also a temperature sensor on the radiator, which signals the driver about the maximum heating of the liquid by means of a device installed in the passenger compartment on the information panel. In most cases, a fan (sometimes two) is attached to the radiator with a casing. The fan is activated automatically when the critical temperature of the coolant is reached, or it works forcibly from the drive with a pump.
The pump provides a constant circulation of coolant throughout the system. The pump receives the energy of rotation by belt transmission from the crankshaft pulley.
The thermostat controls the large and small refrigerant circuit. When starting the engine for the first time, the thermostat starts the fluid in a small circle so that the motor unit warms up to operating temperature faster. After that, the thermostat opens a large circle of the engine cooling system.
Antifreeze or water
Water or antifreeze is used as a coolant. Modern car owners are increasingly using the latter. Water freezes at sub-zero temperatures and is a catalyst in corrosion processes, which negatively affects the system. The only plus is its high heat transfer and, perhaps, affordability.
Antifreeze does not freeze in the cold, prevents corrosion, prevents sulfur deposits in the engine cooling system. But it has lower heat dissipation, which negatively affects during the hot season.
Malfunctions
The consequences of a cooling failure are overheating or overcooling of the engine. Overheating can be caused by insufficient fluid in the system, unstable operation of the pump or fan. Also the malfunction of the thermostat when it should open a large cooling circle.
Malfunctions of the engine cooling system can be caused by severe contamination of the radiator, slagging of the pipes, poor performance of the radiator cap, expansion tank, or poor-quality antifreeze.