ENGINE MANAGEMENT SYSTEM – V, DESCRIPTION AND OPERATION, Bosch ME 7.2 Engine Management System. Operation With the engine running, the coolant pump pulley is driven by an ancillary drive belt. When the engine is cold, the thermostat is closed and coolant is prevented from circulating through the radiator. Coolant is able to circulate through the engine and the passenger compartment heater matrix via a thermostat bypass. As the temperature increases the thermostat begins to open, allowing cool fluid to be drawn from the radiator bottom hose through the pump and into the cylinder block and hot coolant to flow from the coolant pump housing to the radiator via the radiator top hose, where it is cooled by air passing through the matrix. When the thermostat opens fully, the full flow of coolant passes through the radiator. Coolant is also drawn through the liquid cooled transmission fluid cooler and the liquid cooled alternator housing by the coolant pump via the coolant circuit. The increased coolant volume, created by heat expansion, is directed to the expansion tank through a bleed hose from the top of the radiator. The expansion tank has an outlet hose which is connected into the coolant circuit. This outlet hose returns the coolant to the system when the engine cools.
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