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The 7M-G (T) E engine uses a thermostatically controlled water cooling system that is under pressure. The circuit consists of radiator, water pump, thermostat, fans, hoses and other parts. Coolant, which is heated in the water channels that run through the block and head, pumps the system through the radiator. This is supplied by a fan for quick removal of heat. The cooled liquid is then sent back to the engine through the water pump where it can cool it.

The cooler

The radiator takes over the function of extracting heat from the coolant during the flow which it has absorbed by the engine. It is installed directly in front of the engine to use a belt-driven viscous fan. Before it is still the air conditioning dryer, the intercooler and the oil cooler.

The water cooler consists of an upper tank and a lower tank and a core that connects the two tanks. The upper contains the connection to the engine and to the filter. In addition, a hose is attached, can escape through the excess liquid or steam.

The lower tank contains the outlet for the coolant and a drain valve.

The core consists of many tubes through which liquid can flow from the top to the bottom tank and cooling fins that dissipate heat. The air that is blown by the fan through the radiator or the wind make for a quick removal of heat.

Vehicles with automatic transmission also have a transmission fluid cooler installed in the lower tank of the radiator.

radiator cap

The radiator cap is a positive pressure model that seals the radiator. This leads to a pressure build-up in the cooler while the liquid heats up.

This overpressure prevents the coolant from starting to boil, even if the temperature exceeds 1000 ° C. A drain valve (pressure valve) and a vacuum valve (vacuum valve) are installed in the radiator cap. The former opens and discharges steam into the overflow tank as soon as the pressure built up in the cooling system exceeds the limit:

Coolant: 110-1200 ° C
Pressure: 0,65-1.05kg / cm2 (0,6-1,0BAR)

The vacuum valve opens to compensate for the vacuum created in the system, which occurs as soon as the engine is switched off and the temperature of the coolant decreases. The opening of this valve allows the water cooler to independently draw in liquid from the expansion tank again and thus to ensure a consistently high level in the cooler.

surge tank

The surge tank is used to capture the coolant that is forced out of the cooler by thermal expansion. The liquid in the surge tank returns to the cooler as soon as the temperature decreases again - thus avoiding unnecessary loss of coolant.

water pump

The water pump is responsible for the circulation of the coolant through the cooling system. It is located in front of the cylinder block and is driven by a V-ribbed belt.


The thermostat is a wax type and is attached to the water outlet housing. It includes a kind of automatic valve that is controlled by changing the coolant temperature. This valve closes when the temperature drops, preventing water from circulating through the motor - the machine comes up to operating temperature faster. The valve opens as soon as the temperature has risen and allows cooling.

Wax that is located inside the thermostat expands when heated and shrinks when it cools. In the first case, the force of the spring, which keeps the valve closed, is overcome so that it can open. In the second case, the pressure exerted by the wax decreases and the spring closes the valve again. The operating temperature of the thermostat is approx. 880 ° C.