Fig. 5.12. Cooling system: 1 – expansion tank cap; 2 – heater supply hose; 3 – heater outlet hose; 4 – distributor housing; 5 – radiator supply hose; 6 – radiator; 7 – radiator drain hose; 8 – expansion tank steam outlet hose; 9 – water pump; 10 – liquid hose of the expansion tank; 11 – expansion tank
The engine cooling system (Fig. 5.12) is liquid (with forced circulation of liquid), sealed, with an expansion tank.
The system is filled with an ethylene glycol-based liquid (antifreeze) that does not freeze at ambient temperatures down to –40°C.
Note: The procedure for replacing the coolant is described in the subsection "Replacing the coolant".
Attention! It is not recommended to fill the cooling system with water, since the antifreeze contains anti-corrosion and anti-foaming additives, as well as additives that prevent scale deposition.
Warning! Coolant is toxic! Avoid inhalation of vapors and skin contact.
Warning! Repair any leaks in the cooling system promptly to avoid coolant vapors getting into the car's interior during operation. Your health is more valuable than a new cooling system hose or a tube of sealant!
In addition to the radiator, water pump, expansion tank and hoses, the system includes a cast engine cooling jacket surrounding the cylinder walls in the block, combustion chambers and gas passages in the cylinder head, as well as a radiator for the vehicle's interior heater.
The normal thermal mode of the engine is determined by the temperature of the coolant, which is maintained automatically by a thermostat in the range of 90–100°C.
Radiator with horizontal liquid flow, with a tubular-ribbon aluminum core and plastic tanks on the sides. At the bottom of the left tank is a drain cock. The tanks contain the supply and discharge hoses to the engine water jacket.
Expansion tank serves to compensate for the changing volume of the coolant depending on its temperature. The tank is made of translucent plastic. Its walls are marked with "max" and "min" to control the coolant level; on top there is a filler neck, hermetically sealed with a plastic plug with two valves inside it (inlet and outlet), assembled in a single block. The outlet valve opens at a pressure of 120–150 kPa (1.2–1.5 kgf/cm²), ensuring an increase in the boiling point of the coolant and preventing intensive vaporization. When the liquid cools, its volume decreases and a vacuum is created in the system. The inlet valve in the plug opens at a vacuum of about 3 kPa (0.03 kgf/cm²) and lets air into the expansion tank.
Note. The serviceability of the plug valves is very important for the normal operation of the cooling system, but often when problems arise (coolant boiling, etc.), car enthusiasts pay attention only to the operation of the thermostat, forgetting to check the valves. A leaky outlet valve leads to a decrease in the boiling temperature of the coolant, and its jamming in the closed state leads to an emergency increase in pressure in the system, which can cause damage to the radiator and hoses.
Water pump centrifugal type provides forced circulation of liquid in the cooling system, is installed on the front plane of the cylinder block and is driven from the crankshaft pulley by a poly V-belt of the auxiliary drive. The pump has sealed bearings that do not require replenishment of lubricant. The pump is not subject to repair, therefore, in case of failure (fluid leakage or damage to the bearings), it is replaced as an assembly.
Thermostat with a solid temperature-sensitive element maintains the normal operating temperature of the coolant and reduces the engine warm-up time. It is installed in a special socket on the side surface of the cylinder block and is pressed against it by the body. At a coolant temperature of up to 87°C, the thermostat is completely closed and the liquid circulates along a small circuit, bypassing the radiator, which accelerates engine warm-up. At a temperature of 87°C, the thermostat begins to open, and at 102°C it opens completely, ensuring circulation of liquid through the radiator.
Electric fan with a plastic eight-blade impeller provides air blowing through the radiator at low vehicle speeds, mainly in urban conditions or on mountain roads, when the oncoming air flow is insufficient to cool the radiator.
The operation of the electric fan is controlled by the electronic unit of the engine management system, which receives information from the system sensors. The electronic unit turns on the fan at low speed when the coolant temperature is 93°C, at high speed - at 97°C, switches the fan from high speed to low at 94°C, and turns it off at 90°C.
The interior heater radiator is connected to the cooling system via hoses.