Cooling system

The cooling system is designed to maintain normal engine thermal conditions.

When the engine is running, the temperature in the engine cylinders periodically rises above 2000 degrees, and the average temperature is 800–900°C!

If you do not remove heat from the engine, then within a few tens of seconds after starting it will no longer be cold, but hopelessly hot. Next time you can run your cold engine only after it overhaul.

The cooling system is necessary to remove heat from the mechanisms and parts of the engine, but this is only half of its purpose, although the larger half.

To ensure normal operating process, it is also important to speed up the warm-up of a cold engine. And this is the second part of the cooling system.

As a rule, cars use a liquid cooling system, closed type, with forced circulation of liquid and expansion tank(Fig. 29).

The cooling system consists of:

cooling jackets of the block and cylinder head,

centrifugal pump,

thermostat,

radiator with expansion tank,

fan,

connecting pipes and hoses.

In Fig. 29 you can easily distinguish two circles of coolant circulation.

Rice. 29. Engine cooling system diagram: 1 – radiator; 2 – pipe for coolant circulation; 3 – expansion tank; 4 – thermostat; 5 – water pump; 6 – cylinder block cooling jacket; 7 – cooling jacket for the block head; 8 – heater radiator with electric fan; 9 – heater radiator valve; 10 – plug for draining coolant from the block; 11 – plug for draining coolant from the radiator; 12 – fan

The small circulation circle (red arrows) serves to warm up a cold engine as quickly as possible. And when the blue arrows join the red arrows, the already heated liquid begins to circulate in a large circle, cooling in the radiator. Leads this process automatic device – thermostat.

To monitor the operation of the cooling system, there is a coolant temperature indicator on the instrument panel (see Fig. 67). The normal coolant temperature when the engine is running should be between 80–90°C.

Engine cooling jacket consists of many channels in the block and cylinder head through which coolant circulates.

Centrifugal pump causes fluid to move through the engine cooling jacket and the entire system. The pump is driven by a belt drive from a pulley crankshaft engine. The belt tension is adjusted by deflecting the generator housing (see Fig. 63 a) or tension roller drive camshaft engine (see Fig. 11 b).

Thermostat designed to maintain constant optimal thermal conditions of the engine. When starting a cold engine, the thermostat is closed, and all the liquid circulates only in a small circle (Fig. 29 a) to warm it up as quickly as possible. When the temperature in the cooling system rises above 80–85°C, the thermostat automatically opens and some of the liquid enters the radiator for cooling. At high temperatures, the thermostat opens completely, and now all the hot liquid is directed in a large circle for its active cooling.

Radiator serves to cool the liquid passing through it due to the air flow that is created when the car moves or using a fan. The radiator has many tubes and baffles that create a large cooling surface area.

Expansion tank necessary to compensate for changes in the volume and pressure of the coolant during heating and cooling.

Fan designed to forcefully increase the air flow passing through the radiator of a moving car, as well as to create air flow when the car is stationary with the engine running.

Two types of fans are used: a constantly on fan, driven by a belt from the crankshaft pulley, and an electric fan, which turns on automatically when the coolant temperature reaches approximately 100°C.

Pipes and hoses serve to connect the cooling jacket to the thermostat, pump, radiator and expansion tank.

The engine cooling system also includes interior heater. Hot coolant passes through heater radiator and heats the air supplied to the car interior.

The air temperature in the cabin is regulated by a special crane, with which the driver increases or decreases the flow of fluid passing through the heater radiator.

Basic cooling system malfunctions

Coolant leakage may appear as a result of damage to the radiator, hoses, gaskets and seals.

To eliminate the malfunction, it is necessary to tighten the clamps securing the hoses and tubes, and replace the damaged parts with new ones. If the radiator tubes are damaged, you can try to patch holes and cracks, but, as a rule, everything ends with replacing the radiator.

Engine overheating occurs due to insufficient coolant level, weak fan belt tension, clogged radiator tubes, as well as a malfunction of the thermostat.

To eliminate engine overheating, you should restore the fluid level in the cooling system, adjust the fan belt tension, flush the radiator, and replace the thermostat.

Often, engine overheating occurs even when the elements of the cooling system are in working order, when the car moves at low speed and heavy loads on the engine. This occurs when driving in difficult road conditions such as country roads and everyone is tired of city traffic jams. In these cases, it is worth thinking about the engine of your car, and about yourself too, by taking periodic, at least short-term, “breathes”.

Be careful while driving and do not allow emergency mode engine running! Remember that even a one-time overheating of the engine disrupts the structure of the metal, and the life expectancy of the “heart” of the car is significantly reduced.

Cooling System Operation

When operating your vehicle, you should periodically look under the hood. A timely detection of a malfunction in the cooling system will allow you to avoid major engine repairs.

If coolant level in the expansion tank has dropped or there is no liquid at all, then first you need to add it, and then you should figure out (on your own or with the help of a specialist) where it went.

During engine operation, the liquid heats up to a temperature close to its boiling point. This means that the water contained in the coolant will gradually evaporate.

If in six months daily use car, the level in the tank has dropped a little, this is normal. But if yesterday the tank was full, and today there is only the bottom in it, then you need to look for a coolant leak.

Leakage of fluid from the system can be easily identified by dark spots on the asphalt or snow after a more or less long period of parking. By opening the hood, you can easily find the location of the leak by comparing wet marks on the asphalt with the location of the cooling system elements under the hood.

The fluid level in the tank must be monitored at least once a week. If the level has noticeably decreased, then the reason for its decrease must be determined and eliminated. In other words, the cooling system must be put in order, otherwise the engine may become seriously ill and require “hospitalization.”

Almost all domestic cars a special low-freezing liquid called Antifreeze A-40. Number 40 shows the negative temperature at which the liquid begins to freeze (crystallize). In the Far North it is used Antifreeze A-65, and accordingly it begins to freeze at a temperature of minus 65°C.

Antifreeze is a mixture of water with ethylene glycol and additives. This solution combines a lot of advantages. Firstly, it begins to freeze only after the driver himself has already frozen (just kidding), and secondly, Antifreeze has anti-corrosion, anti-foaming properties and practically does not produce deposits in the form of ordinary scale, since it contains pure distilled water . That's why Only distilled water can be added to the cooling system.

When operating a vehicle, it is necessary control not only the tension, but also the condition of the water pump drive belt, since its breakdown on the road is always unpleasant. It is recommended to have a spare belt in your travel kit. If not you yourself, then some kind person will help you change it.

The coolant may boil and cause engine damage if it fails. fan electric drive sensor. If the electric fan does not receive a command to turn on, the liquid continues to heat up, approaching the boiling point, without cooling assistance.

But the driver has before his eyes a device with an arrow and a red sector! Moreover, almost always when the fan is turned on, a slight additional noise is felt. There would be a desire to control, but there will always be ways.

If on the road (or more often in a traffic jam) you notice that the coolant temperature is approaching critical and the fan is running, then in this case there is a way out. It is necessary to include an additional radiator in the operation of the cooling system - the interior heater radiator. Fully open the heater tap, turn on the heater fan at full speed, lower the door windows and “sweat” home or to the nearest car service center. But at the same time, continue to closely monitor the engine temperature gauge needle. If she does enter the red zone, stop immediately, open the hood and “cool down”.

Can cause trouble over time thermostat, if it stops releasing liquid through a large circulation circle. Determining whether the thermostat is working is not difficult. The radiator should not heat up (determined by hand) until the coolant temperature gauge needle reaches the middle position (thermostat closed). Later, hot liquid will begin to flow into the radiator, quickly heating it, which indicates the timely opening of the thermostat valve. If the radiator continues to remain cold, then there are two options. Tap on the thermostat housing, maybe it will open after all, or immediately, mentally and financially, prepare to replace it.

Immediately "surrender" to a mechanic if you see droplets of liquid on the oil dipstick that have entered the lubrication system from the cooling system. It means that Damaged cylinder head gasket and coolant leaks into the engine oil pan. If you continue to operate the engine with oil half consisting of antifreeze, the wear of engine parts will become catastrophic.

Water pump bearing It doesn’t break “suddenly”. First, a specific whistling sound will appear from under the hood, and if the driver “thinks about the future,” he will replace the bearing in a timely manner. Otherwise, it will still have to be changed, but with the consequence of being late for the airport or for a business meeting, due to a “suddenly” broken down car.

Each driver must know and remember that When the engine is hot, the cooling system is under high pressure!

If the engine of your car overheats and “boils,” then, of course, you need to stop and open the hood of the car, but you should not open the radiator cap or expansion tank. This will do practically nothing to speed up the engine cooling process, and you can get severe burns.

Everyone knows what a clumsily opened bottle of champagne means for smartly dressed guests. In a car everything is much more serious. If you quickly and thoughtlessly open the cap of a hot radiator, a fountain will fly out, but not of wine, but of boiling Antifreeze! In this case, not only the driver, but also nearby pedestrians may suffer. Therefore, if you ever have to open the radiator cap or expansion tank, you should first take precautions and do it slowly.

Strictly speaking, the term “liquid cooling” is not entirely correct, since the liquid in the cooling system is just an intermediate coolant that penetrates the thickness of the walls of the cylinder block. The role of the removal agent in the system is played by the air blowing on the radiator, so cooling modern car It would be more correct to call it hybrid.

Liquid cooling system design

The liquid engine cooling system consists of several elements. The most complex one is called the “cooling jacket”. This is an extensive network of channels in the thickness of the cylinder block and. In addition to the jacket, the system includes a cooling system radiator, expansion tank, water pump, thermostat, metal and rubber connecting pipes, sensors and control devices.

Propylene glycol is the basis of coolant (antifreeze) and is approved by veterinarians food supplement for dog diet

The system is built on the principle of forced circulation, which is provided by a water pump. Thanks to the constant outflow of heated fluid, the engine is cooled evenly. This explains the use of the system in the vast majority of modern cars.

After passing through the channels in the walls of the block, the liquid heats up and enters the radiator, where it is cooled by the air flow. When the car is moving, natural airflow is sufficient for cooling, and when the car is stationary, airflow occurs due to an electric fan, which is turned on by a signal from the temperature sensor.

Learn about the Key Elements of Water Cooling

Cooling radiator

A radiator is a panel of small-diameter metal tubes coated with aluminum or copper “finning” to increase the heat transfer area. In essence, the plumage is a repeatedly folded ribbon of metal. The total total area of ​​the tape is quite large, which means it can release quite a lot of heat into the atmosphere per unit time.

The most vulnerable element of the engine design is the turbocharger (turbine), operating at extremely high high speed. If overheated, destruction of the impeller and shaft bearings is almost inevitable

Thus, the heated liquid inside the radiator circulates simultaneously through all the numerous thin tubes and is cooled quite intensively. There is a safety valve in the radiator filler cap that removes vapors and excess liquid that expands when heated.

Depending on the mode internal combustion engine operation The cycle of movement of coolant in the system may change. The volume of liquid circulating in each circle directly depends on the extent to which the main and additional thermostat valves are open. This scheme provides automatic support for optimal temperature regime engine operation.

Advantages and disadvantages of a liquid cooling system

Main advantage liquid cooling lies in the fact that the engine is cooled more evenly than in the case of blowing the block with air flow. This is explained by the greater heat capacity of the coolant compared to air.

The liquid cooling system can significantly reduce the noise from a running engine due to the greater thickness of the block walls.

The inertia of the system does not allow the engine to cool quickly after switching off. Heated vehicle fluid and for preheating the combustible mixture.

Along with this, the liquid cooling system has a number of disadvantages.

The main disadvantage is the complexity of the system and the fact that it operates under pressure after the fluid has warmed up. Liquid under pressure places increased demands on the tightness of all connections. The situation is complicated by the fact that the operation of the system involves constant repetition of the “heating - cooling” cycle. This is harmful to connections and rubber pipes. When heated, rubber expands and then contracts as it cools, which causes leaks.

In addition, the complexity and large number of elements in itself serves as a potential cause of “man-made disasters”, accompanied by “boiling” of the engine in the event of failure of one of the key parts, for example, a thermostat.

I suggest you first consider schematic diagram cooling systems.

1 - heater; 2 - engine; 3 - thermostat; 4 - pump; 5 - radiator; 6 - plug; 7 - fan; 8 - expansion tank;
A - small circulation circle (thermostat closed);
A+B - large circulation circle (thermostat open)

Liquid circulation in the cooling system is carried out in two circles:

1. Small circle- the liquid circulates when starting a cold engine, ensuring its rapid warm-up.

2. Big circle- the movement circulates when the engine is warm.

To put it simply, the small circle is the circulation of coolant WITHOUT the radiator, and the large circle is the circulation of coolant THROUGH the radiator.

The design of the cooling system varies depending on the car model, however, the principle of operation is the same.

So, the start of operation of the cooling system occurs when the heart of this system, the liquid pump, starts.

Liquid pump

The liquid pump provides forced circulation of liquid in the engine cooling system. Centrifugal-type vane pumps are used on car engines.

You should look for our liquid pump or water pump on the front of the engine (the front part is the one that is closer to the radiator and where the belt/chain is located).

The liquid pump is connected by a belt to crankshaft and a generator. Therefore, to find our pump, it is enough to find the crankshaft and find the generator. We'll talk about the generator later, but for now I'll just show you what to look for. The generator looks like a cylinder attached to the engine body:

1 - generator; 2 - liquid pump; 3 - crankshaft

So, we figured out the location. Now let's look at its device. Let us remind you that the structure of the entire system and its parts is different, but the operating principle of this system is the same.

1 - Pump cover; 2 - Thrust seal ring of the oil seal.
3 - Oil seal; 4 - Pump roller bearing.
5 - Fan pulley hub; 6 - Locking screw.
7 - Pump roller; 8 - Pump housing; 9 - Pump impeller.
10 - Intake pipe.

The operation of the pump is as follows: the pump is driven from the crankshaft through a belt. The belt turns the pump pulley, rotating the pump pulley hub (5). This, in turn, rotates the pump shaft (7), at the end of which there is an impeller (9). The coolant enters the pump housing (8) through the inlet pipe (10), and the impeller moves it into the cooling jacket (through a window in the housing, as can be seen in the figure, the direction of movement from the pump is shown by an arrow).

Thus, the pump is driven by the crankshaft; liquid enters it through the inlet pipe and goes into the cooling jacket.

Let's now see where the liquid comes from into the pump? And the liquid flows through a very important part - the thermostat. It is the thermostat that is responsible for the temperature regime.

Thermostat

The thermostat automatically adjusts the water temperature to speed up the engine warm-up after starting. It is the operation of the thermostat that determines in which circle (large or small) the coolant will flow.

This unit looks something like this in reality:

Thermostat operating principle very simple: the thermostat has a sensitive element, inside of which there is a solid filler. At a certain temperature, it begins to melt and opens the main valve, and the additional one, on the contrary, closes.

Thermostat device:

1, 6, 11 – pipes; 2, 8 – valves; 3, 7 – springs; 4 – balloon; 5 – diaphragm; 9 – rod; 10 – filler

The thermostat has two inlet pipes 1 and 11, an outlet pipe 6, two valves (main 8, additional 2) and a sensitive element. The thermostat is installed in front of the coolant pump inlet and is connected to it through pipe 6.

Compound:

Throughpipe 1 connects Withengine cooling jacket,

Through pipe 11- with the bottom diverting radiator tank.

The sensitive element of the thermostat consists of a cylinder 4, a rubber diaphragm 5 and a rod 9. Inside the cylinder between its wall and the rubber diaphragm there is a solid filler 10 (fine-crystalline wax), which has a high coefficient of volumetric expansion.

The main valve 8 of the thermostat with spring 7 begins to open when the coolant temperature exceeds 80 °C. At temperatures below 80 °C, the main valve closes the fluid outlet from the radiator, and it flows from the engine to the pump, passing through the open additional valve 2 of the thermostat with spring 3.

When the temperature of the coolant increases above 80 °C, the solid filler melts in the sensitive element and its volume increases. As a result, the rod 9 comes out of the cylinder 4, and the cylinder moves upward. At the same time, additional valve 2 begins to close and, at temperatures above 94 °C, blocks the passage of coolant from the engine to the pump. The main valve 8 in this case opens completely and the coolant circulates through the radiator.

The operation of the valve is clearly and clearly shown in the figure below:

A - small circle, the main valve is closed, the bypass valve is closed. B - large circle, the main valve is open, the bypass valve is closed.

1 - Inlet pipe (from the radiator); 2 - Main valve;
3 - Thermostat housing; 4 - Bypass valve.
5 - Overflow hose connection.
6 - Coolant supply pipe to the pump.
7 - Thermostat cover; 8 - Piston.

So, we dealt with the small circle. We disassembled the device of the pump and thermostat, connected to each other. Now let's move on to the big circle and the key element of the big circle - the radiator.

Radiator/cooler

Radiator provides heat removal from the coolant to environment. On passenger cars Tubular-plate radiators are used.

So, there are 2 types of radiators: collapsible and non-collapsible.

Below is their description:

I want to say again about the expansion tank (expansion Tank)

A fan is installed next to the radiator or on it. Let's now move on to the design of this very fan.

Fan

The fan increases the speed and amount of air passing through the radiator. Four- and six-bladed fans are installed on car engines.

If a mechanical fan is used,

The fan includes six or four blades (3) riveted to the crosspiece (2). The latter is screwed to the fluid pump pulley (1), which is driven by the crankshaft using a belt drive (5).

As we said earlier, the generator (4) is also engaged.

If using an electric fan,

then the fan consists of an electric motor 6 and a fan 5. The fan is four-bladed, mounted on the electric motor shaft. The blades on the fan hub are located unevenly and at an angle to the plane of its rotation. This increases the fan flow and reduces the noise of its operation. For more efficient work The electric fan is housed in casing 7, which is attached to the radiator. The electric fan is attached to the casing using three rubber bushings. The electric fan is switched on and off automatically by sensor 3 depending on the coolant temperature.

So let's summarize. Let's not be unfounded and sum it up using some picture. There is no need to focus on specific device, but the principle of operation must be understood, because it is the same in all systems, no matter how different their structure is.

When the engine starts, the crankshaft begins to rotate. Through a belt drive (let me remind you that the generator is also located on it) rotation is transmitted to the liquid pump pulley (13). It rotates the shaft with the impeller inside the liquid pump housing (16). The coolant enters the engine cooling jacket (7). Next, through the outlet pipe (4), the coolant returns to the liquid pump through the thermostat (18). At this time, the bypass valve in the thermostat is open, but the main valve is closed. Therefore, the liquid circulates through the engine jacket without the participation of the radiator (9). This ensures quick warm-up of the engine. Once the coolant is heated, the main thermostat valve opens and the bypass valve closes. Now the fluid cannot flow through the thermostat bypass pipe (3) and is forced to flow through the inlet pipe (5) into the radiator (9). There the liquid cools and flows back into the liquid pump (16) through the thermostat (18).

It is worth noting that some of the coolant flows from the engine cooling jacket into the heater through pipe 2 and returns from the heater through pipe 1.

Every car uses an engine internal combustion. Widespread fluid systems cooling - only on old "Zaporozhets" and new "Tata" air blowing is used. It should be noted that the circulation scheme on all machines is almost similar - the same elements are present in the design, they perform identical functions.

Small cooling circle

In the cooling system circuit of an internal combustion engine, there are two circuits - small and large. In some ways it is similar to human anatomy - the movement of blood in the body. The liquid moves in a small circle when it is necessary to quickly warm up to operating temperature. The problem is that the motor can function normally in a narrow temperature range - about 90 degrees.

You cannot increase or decrease it, as this will lead to violations - the ignition timing will change, fuel mixture will burn out untimely. The interior heater radiator is included in the circuit - after all, it is necessary that the inside of the car be warm as early as possible. The supply of hot antifreeze is turned off using a tap. The location of its installation depends on the specific car - on the partition between the passenger compartment and engine compartment, in the glove compartment area, etc.

Large cooling circuit

At the same time, the main radiator is also turned on. It is installed in the front of the car and is designed to urgently reduce the temperature of the fluid in the engine. If the car has an air conditioner, then its radiator is installed nearby. On Volga and Gazelle cars, an oil cooler is used, which is also installed in the front of the car. The radiator is usually equipped with a fan, which is driven by an electric motor, belt or clutch.

Liquid pump in the system

This device is included in the coolant circulation circuit of the Gazelle and any other car. The drive can be carried out as follows:

1. From the timing belt.
2. From the generator belt.
3. From a separate belt.

The structure consists of the following elements:

1. Metal or plastic impeller. The efficiency of the pump depends on the number of blades.
2. The body is usually made of aluminum and its alloys. The fact is that this particular metal works well in aggressive conditions; corrosion has practically no effect on it.
3. The pulley for installing the drive belt is toothed or wedge-shaped.
4. The shaft is a steel rotor, at one end of which there is an impeller (inside), and on the outside there is a pulley for installing the drive pulley.
5. Bronze bushing or bearing - these elements are lubricated using special additives found in antifreeze.
6. The oil seal prevents fluid from leaking out of the cooling system.

Thermostat and its features

It is difficult to say which element ensures the most efficient circulation of fluid in the cooling system. On the one hand, the pump creates pressure and antifreeze moves through the pipes with its help.

But on the other hand, if there were no thermostat, the movement would occur exclusively in a small circle. The design contains the following elements:

1. Aluminum housing.
2. Outputs for connecting to pipes.
3. Bimetal type plate.
4. Mechanical valve with return spring.

The principle of operation is that at temperatures below 85 degrees the liquid moves only along a small circuit. In this case, the valve inside the thermostat is in a position in which antifreeze does not enter the large circuit.

As soon as the temperature reaches 85 degrees, it begins to deform. It acts on the mechanical valve and allows antifreeze access to the main radiator. As soon as the temperature drops, the thermostat valve will return to its original position under the action of the return spring.

Expansion tank

The cooling system of an internal combustion engine has an expansion tank. The fact is that any liquid, including antifreeze, increases in volume when heated. And when cooled, the volume decreases. Therefore, some kind of buffer is needed in which a small amount of liquid will be stored so that there is always enough of it in the system. It is this task that the expansion tank copes with - excess spills out there during heating.

Expansion tank cap

Another irreplaceable component of the system is the plug. There are two types of construction - sealed and non-sealed. If the latter is used on the car, the expansion tank plug has only a drainage hole through which the pressure in the system is balanced.

But if a sealed system is used, then there are two valves in the plug - an inlet (takes air from the atmosphere inside, operates at a pressure below 0.2 bar) and an outlet (operates at a pressure above 1.2 bar). It removes excess air from the system.

It turns out that the pressure in the system is always greater than in the atmosphere. This allows you to slightly increase the boiling point of the antifreeze, which has a beneficial effect on engine performance. This is especially good for driving through traffic jams in urban environments. An example of a sealed system is VAZ-2108 and similar cars. Unsealed - models of the classic VAZ series.

Radiator and fan

The coolant circulates through the main radiator, which is installed at the front of the car. This location was not chosen by chance - when driving at high speed, the radiator honeycombs are blown by a counter flow of air, which reduces the engine temperature. A fan is installed on the radiator. Most of these devices have On Gazelles, for example, clutches similar to those installed on air conditioning compressors are often used.

The electric fan is turned on using a sensor installed at the bottom of the radiator. Can be used on injection machines signal from the temperature sensor, which is located on the thermostat housing or in the engine block. The most simple circuit switch contains only one thermal switch - its contacts are normally open. As soon as the temperature at the bottom of the radiator reaches 92 degrees, the contacts inside the switch will close and voltage will be supplied to the fan motor.

Interior heater

This is the most important part when viewed from the driver and passengers' perspective. Comfort when driving in the winter season depends on the efficiency of the stove. The heater is part of the coolant circulation circuit and consists of the following components:

1. Electric motor with impeller. It is turned on according to a special circuit in which there is a constant resistor - it allows you to change the rotation speed of the impeller.
2. The radiator is the element through which hot antifreeze passes.
3. The tap is designed to open and close the supply of antifreeze inside the radiator.
4. The duct system allows you to direct hot air in the desired direction.

The coolant circulation pattern through the system is such that if only one inlet to the radiator is closed, hot antifreeze will not get into it in any way. There are cars in which there is no heater tap - there is always hot antifreeze inside the radiator. And in summer time The air ducts simply close and no heat is supplied to the cabin.

This is why cars have an engine cooling system. A centrifugal pump forces fluid to move through the engine cooling jacket and the entire system. Operation of the cooling system. The engine cooling jacket is the channels in the block and cylinder head.

Thermostat 7. Regulates circulation in a small or large circle depending on the temperature. Circulation through the stove occurs constantly, regardless of the position of the thermostat and the circle in which the liquid circulates.

Pressure in the system is needed in order to increase the boiling point. Even when the temperature reaches 110 degrees, the liquid in the system does not boil. We started the cold engine. Immediately we have coolant circulating in the system. Liquid circulation is created by pump 6 (Fig. 1), driven timing belt or a separate belt.

The liquid will circulate according to the following pattern until it reaches a certain temperature. After which thermostat 7 will close the small circle and open the large one. The cooled liquid is pumped back into the engine. If the natural cooling of the liquid in the radiator is not enough and the coolant temperature continues to rise, then the fan switch sensor 4, located at the bottom of the radiator, is triggered.

At this temperature, optimal temperatures are established in the engine. thermal clearances, the engine develops maximum power, fuel consumption becomes nominal. Under the guidance of the thermostat, 2 circulation circles perform their functions (Figure 7.1). The small circle performs the function of heating the engine. After heating, the liquid begins to circulate in a large circle and cools in the radiator.

Coolant circulates through these channels. The radiator consists of many tubes that form a large cooling surface. This is where the liquid cools. Expansion tank. With its help, the volume of liquid is compensated when it heats up and cools down.

The next time you can start your cold engine only after it has been overhauled. The cooling system is needed to remove heat from the mechanisms and parts of the engine, but this is only half of its purpose, although it is the larger half. To ensure a normal operating process, it is also important to speed up the warm-up of a cold engine. In Figure 25 you can easily distinguish two circles of coolant circulation.

Engine cooling system diagram.

And when the blue arrows join the red arrows, the already heated liquid begins to circulate in a large circle, cooling in the radiator. To monitor the operation of the system, there is a coolant temperature indicator on the instrument panel. The pump is driven by a belt drive from the engine crankshaft pulley. When starting a cold engine, the thermostat is closed, and all the liquid circulates only in a small circle (Fig. 25) to warm it up as quickly as possible.

At high temperatures, the thermostat opens completely and all the hot liquid is directed in a large circle for its active cooling. The radiator serves to cool the liquid passing through it due to the air flow that is created when the car is moving or using a fan. The radiator has many tubes and "membranes" that create a large cooling surface area.

Cooling systems of different designs

The expansion tank is necessary to compensate for changes in the volume and pressure of the coolant during heating and cooling. Pipes and hoses are used to connect the engine cooling jacket to the thermostat, pump, radiator and expansion tank. Hot coolant passes through the heater core and heats the air supplied to the vehicle interior. The air temperature in the cabin is regulated by a special tap, with which the driver increases or decreases the flow of liquid passing through the heater radiator.

In other words, you need to put your engine cooling system in order. When the temperature in the cooling system rises above 80 - 85O, the thermostat automatically opens and part of the liquid enters the radiator for cooling. And this is the second part of the cooling system. The thermostat is designed to maintain a constant optimal thermal condition of the engine. Maintains a certain pressure in the cooling system.