Engine cooling system
All models of the vehicles considered in this Manual are equipped with a positive pressure engine cooling system with thermostatic control of the working fluid circulation. The rotary water pump is mounted on the engine block and pumps the coolant through the cooling tract of the latter (for details on installing the water pump, see Section Removal and installation the water pump). The flow of liquid washes the areas of each cylinder in the block, after which it is directed to the rear of the engine. Cooling channels laid in the block and cylinder head casting provide intensive cooling of the intake and exhaust ports, spark plug installation areas and exhaust valve guides.
A wax-filled thermostat controls the engine operating temperature during its warm-up. In the first minutes after starting a cold engine, the thermostat remains closed, thereby preventing the circulation of coolant through the radiator. As the engine temperature approaches the normal operating value, the thermostat valve gradually opens, connecting the radiator to the cooling circuit, ensuring maximum intensity of heat removal from the working fluid (coolant).
The cooling system has a hermetically sealed design and is tightly closed by a radiator cap capable of withstanding a certain excess pressure, which increases the boiling point of the coolant and, accordingly, the efficiency of heat removal through the radiator. When the internal pressure in the system exceeds a certain value, the spring-loaded plate of the safety valve mounted in the radiator cap rises above its seat, ensuring the flow of excess coolant through the connecting (overflow) tube into the expansion tank. As the system cools down, the liquid automatically returns from the tank to the radiator.
Adding coolant to the system is done through the neck of the expansion tank (see Chapter Settings and ongoing maintenance), which simultaneously also acts as a receiver, accumulating the excess liquid displaced from the radiator.
Due to the listed design features, such a cooling system is called closed, since it excludes any functional losses of the working fluid.
Heating system
The main components of the interior heating system are an electric fan and a heat exchanger placed in a box-shaped heater casing, fixed under the vehicle's instrument panel. The heat exchanger is connected to the engine cooling system via rubber hoses. The heater/air conditioner control unit is mounted in the vehicle's instrument panel. The coolant heated in the engine circulates through the heater heat exchanger, giving off its heat to the air filling the casing. When the interior heating is switched on, the plate damper opens, as a result of which the internal volume of the heater casing is connected to the interior volume. When the fan is switched on, the impeller of the latter begins to drive the air supplied to the interior through the heat exchanger, ensuring its intensive heating.
Air conditioning system
The air conditioning system consists of a condenser installed in front of the radiator, an evaporator located next to the heater heat exchanger, a compressor mounted on the engine block, and a filter receiver-dryer (accumulator) equipped with a high-pressure reducing valve. All components are connected to each other by refrigeration lines.
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The fan drives the air entering the cabin through the evaporator heat exchanger, which operates in the opposite mode to the radiator. The refrigerant pumped through the heat exchanger boils and, evaporating, takes excess heat from the air. The temperature inside the cabin decreases to the required comfortable value (at the operator's choice). The compressor maintains the circulation of the refrigerant in the system, pumping the heated liquid through the condenser, where it cools and flows back to the evaporator.