The engine cooling system uses special fluids based on a mixture of water and ethylene glycol. They have a low freezing point and a high boiling point. In addition, thanks to the complex of added additives, the coolant prevents corrosion of the channel walls, does not foam, and extends the service life of the coolant pump seal.
The circulation of liquid in the system is provided by a centrifugal pump installed in the cylinder block. The pump is driven by a timing belt.
The cooling system consists of two so-called circulation circles. The small circle does not include the engine radiator, and the liquid washes only the cylinder block and cylinder head, and also flows through the throttle body channel and the heater radiator. The heater radiator is built into the engine cooling system and is designed to heat the interior by circulating hot coolant through it. When moving in a large circle, the coolant passes through the engine radiator, where it is cooled by the oncoming air flow. The thermostat controls the direction of fluid flow in the engine cooling system. It has two valves installed - the main one and the bypass one (additional). The main valve controls the circulation of fluid in a large circle, and the bypass valve controls the circulation in a small circle. The valves are interconnected: when one opens, the other closes, and vice versa.
On a cold engine, the bypass valve (additional) the thermostat valve is open and the liquid circulates only in a small circle. At a temperature of about 87°C, the main thermostat valve begins to open and the bypass valve begins to close, and for some time the liquid circulates in the small and large circles simultaneously. At 102°C, the main thermostat valve is fully open and the bypass valve is closed, and all fluid flows through the engine radiator. If the air flow is not intense enough, the radiator is cooled by an electric fan. It is installed behind the engine radiator and is switched on by a signal from the electronic engine control unit. An additional resistor is built into the fan motor power supply circuit.
To compensate for thermal expansion of the liquid, an expansion tank is installed in the cooling system. The tank cap contains inlet and outlet safety valves, which allows maintaining optimal pressure in the system when the liquid is heated, and also compensates for the vacuum when it cools.
Cooling system:
1 - coolant drain hose from the heater radiator;
2 - coolant supply hose to the heater radiator;
3 - coolant pump inlet pipe hose;
4 - expansion tank hose;
5 - expansion tank;
6 - engine radiator steam outlet hose;
7 - thermostat;
8 - hose for supplying liquid to the throttle assembly;
9 - hose for supplying liquid to the engine radiator;
10 - hose for draining liquid from the engine radiator;
11 - engine radiator;
12 - radiator drain plug;
13 - radiator electric fan;
14 - Coolant pump;
15 - Coolant pump inlet pipe;
16 - coolant drain hose from the throttle assembly.
(Original text is available on the website LADAMAN.ru)