AIR CONDITIONING, DESCRIPTION AND OPERATION, Description. For additional airflow through the radiator matrix, particularly when the vehicle is stationary, two cooling fans are fitted. A viscous fan is attached to the coolant pump pulley at the front of the engine. The fan is attached to a threaded spigot on the pulley with a left hand threaded nut. The fan draws air through the radiator to assist in cooling when the vehicle is stationary. An electric fan controlled by the Electronic Diesel Control (EDC) system is fitted in front of the radiator assembly. It is controlled by the Engine Control Module (ECM) via a cooling fan ECU. The cooling fan ECU is located behind the radiator, below the bonnet closing panel. The temperature of the cooling system is monitored by the ECM via signals from an Engine Coolant Temperature (ECT) sensor, which is mounted at the rear of the cylinder head. Operation With the engine running, the coolant pump pulley is driven by the 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 bypass, heater matrix and coolers.
COOLING SYSTEM – TD6 DESCRIPTION AND OPERATION 26-1-9 As the temperature increases, at 88 CF) the thermostat begins to open, bleeding cool fluid from the radiator bottom hose through the pump and into the cylinder block. This allows hot coolant to flow from the cylinder block to the radiator through the top hose, balancing the flow of hot and cold fluid to maintain the optimum operating temperature. When the thermostat opens fully, the full flow of coolant passes through the radiator. 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. Coolant flows through the radiator from the top right hand tank to the bottom left hand tank and is cooled by air passing through the matrix. The temperature of the cooling system is monitored by the ECM via a temperature sensor located in the cylinder head. The ECM uses signals from this sensor to control the cooling fan operation and adjust fuelling according to engine temperature +