The engine cooling system consists of the following main elements: radiator, water pump, thermostat and radiator fan.
The coolant must provide cooling and anti-corrosion action all year round. Before the winter period begins, the concentration of the coolant should be checked.
The liquid, which expands when heated, accumulates in the expansion tank and, after the engine cools, flows back into the cooling circuit.
As a result, the circuit remains constantly filled and cooling is complete.
The reservoir cap contains a safety valve that ensures a constant pressure in the cooling system of approximately 1.3 bar and a boiling point of the coolant of approximately 125°C.
To avoid compression of the coolant hoses when the engine cools, the cap also has a low-pressure valve that opens when the pressure in the system drops to approximately 0.10 bar and lets air into the cooling system.
The liquid in the radiator is cooled by the oncoming air flow when the car is moving or by the air flow from an electric fan. The coolant is taken from the lower radiator tank by the water pump through the lower hose and fed into the cooling jacket of the cylinder head and block.
The design of the cylinder head is such that the cooling channels pass next to the valve seats and form a zone of intensive cooling. From here, the coolant enters the cylinder block, and from the block - into the thermostat and the upper radiator tank, from where a new cooling cycle begins.
When the coolant temperature is below 92°C, the thermostat is closed. In this case, the coolant is supplied to the circuit through the bypass channel of the water pump and is taken by the pump from the thermostat housing. This ensures rapid and uniform warming up of the engine. At 92°C, the thermostat begins to open and coolant begins to circulate through the radiator, dissipating heat into the air.
Additional cooling of the liquid is provided by a radiator fan driven by an electric motor. The models under consideration are equipped with two radiator fans.
As soon as the coolant temperature rises to 100°C, the relay turns on the radiator blower electric fan; as the coolant temperature decreases, the electric fan automatically turns off.
On vehicles with a 3.2 l petrol engine (6VD1-W), the radiator fan is driven by a viscous coupling.
Precautions:
- When opening the expansion tank cap on a hot engine, care must be taken as escaping hot vapors and coolant can cause severe burns. In case the radiator filler cap must be removed before the engine and radiator have completely cooled down (although this is not recommended), first of all, it is necessary for the pressure in the cooling system to decrease. To avoid getting burned, cover the lid with a thick piece of cloth and slowly unscrew it until you hear a hissing sound. When the hissing stops, indicating that the pressure has reduced, continue to slowly unscrew the cap until it can be removed. If the hissing noise continues, wait until it completely disappears. Always try to keep your face and hands at a safe distance when opening the cap.
- Avoid contact of antifreeze with skin or painted surfaces of the vehicle. Wash off any spilled liquid immediately with water. Never allow antifreeze to sit in an open container or spill on the driveway or garage floor.
- If the engine is hot, the electric fan may turn on even when the engine is off.
- Different antifreezes provide different levels of corrosion protection and compatibility with light metals. If you choose the wrong antifreeze, this will lead to significant subsequent repair costs. If you cannot completely replenish the old antifreeze, it is better to completely replace the coolant.
Do not add cold water to the cooling system of a hot engine
If the engine cooling system has lost too much coolant during a trip, do not add cold water to the expansion tank under any circumstances. A hot engine can suffer thermal shock from adding cold water, and in extreme cases the cylinder block can be torn apart or the cylinder head can be deformed. In this case, the engine cannot be used further, since the cylinder head gasket will not be able to fit tightly to the cylinder block, and the coolant will leak out of the block or mix with the engine oil, resulting in an emulsion that will damage the engine. Therefore, wait for some time to cool down the engine and only then add water. In any case, you will then need to contact a specialist to determine the cause of the loss of coolant.
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