General information
The cooling system operates under excess pressure. It consists of a water pump, an aluminum radiator, a fan and a thermostat.
The system works as follows. Cold liquid from the lower radiator tank enters through the lower hose to the inlet of the water pump, which pumps it through the cavities and channels of the block and cylinder head. after cooling the cylinders. surfaces of the combustion chambers, valve seats, the liquid enters the thermostat, which is initially closed. The liquid passes through the heater heat exchanger and returns through the cylinder block to the pump.
Until the engine has warmed up, the coolant circulates only through the block and cylinder head, as well as through the heater. When the liquid is heated to a certain temperature, the thermostat opens and the liquid enters the radiator through the upper hose. On some models, the opening and closing of the thermostat is carried out at the command of the electronic engine control unit. Such a system allows you to more accurately maintain the operating temperature of the engine, the composition of the fuel-air mixture, and reduce the concentration of harmful emissions into the atmosphere. In the radiator, the liquid is cooled by the air flow passing through it when the car is moving. If necessary, the air flow is created by the fan, the cooled liquid is drained into the lower tank of the radiator, from where it is again sucked in by the water pump and the cycle is repeated.
Depending on the model, the car may be equipped with one of two types of fan. Models with a 4-cylinder engine and a 6-cylinder M54 engine have an electrically driven fan located behind the radiator. On models with a 6-cylinder M52TU engine, the fan is driven by a belt from the crankshaft through a viscous coupling. The viscous clutch changes the fan speed depending on the engine temperature. At low temperatures, the clutch creates little engagement between the fan shaft and its drive, so that the fan rotates slowly. As the temperature rises, the coupling property increases and the fan starts to rotate faster and faster. On such models, an additional electric fan is installed in front of the radiator.
A description of the air conditioning system is given in paragraph 11.
Precautionary measures
Attention! Do not attempt to remove the expansion tank cap or disconnect any of the coolant hoses while the engine is warm, as there is a high risk of burns. If the bottle cap needs to be threaded off before the engine and radiator are completely cool (even if it's not recommended), you must first reduce the pressure in the cooling system. To avoid burns, cover the cap with a thick cloth and slowly unscrew it until a hissing sound is heard. When the hissing stops, which means a decrease in pressure, slowly unscrew the reservoir cap to the end and remove it; if the hissing sounds are still heard, wait for them to stop. In all cases, when opening the cap of the expansion tank, try to keep a distance from it and protect your hands.
Attention! Do not allow antifreeze to come into contact with your skin or painted body surfaces. If this does happen, immediately wash off the spilled liquid with plenty of water. Never leave antifreeze in an open container or in a puddle on the garage floor. Children and pets may be attracted to the pleasant smell, but if ingested, antifreeze is deadly.
Attention! When working on models. equipped with air conditioning, observe the additional precautions in paragraph 11.