Cooling system operation (Cooling system - K Series) (page 2 of 2)

The cooling system employed is the by-pass type, allowing coolant to circulate around the engine and the heater circuit while the thermostat is closed.

The thermostat is installed in a housing which is attached to the coolant pump. The thermostat is located in the inlet side of the cooling circuit, which provides a more stable control of the coolant temperature in the engine.

When cold, the thermostat is closed and coolant is prevented from circulating through the radiator. Coolant is able to circulate through the bypass and heater circuits.

As the temperature increases, the thermostat gradually opens, bleeding cool fluid from the radiator bottom hose into the cylinder block and allowing hot coolant to flow to the radiator through the radiator 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.

An expansion tank is fitted to the right hand shock absorber mounting. Any excess coolant, created by heat expansion, is returned to the expansion tank through bleed lines from the top of the radiator and from the cylinder block. The expansion tank has an outlet pipe which is connected into the coolant circuit. The outlet pipe supplies coolant into the system when the engine is cool. This replaces coolant displaced to the expansion tank due to heat expansion.

The coolant is circulated by a rotor type pump. The pump is mounted at the rear of the engine and is driven by a geared pulley from the camshaft timing belt. The pump draws coolant from the radiator bottom hose and circulates it through the engine and heater circuit.

The radiator, positioned at the front of the vehicle, is a copper/brass cross - flow type with moulded plastic end tanks. The radiator is mounted in rubber bushes; the bottom of the radiator is located in the front body cross member, and the top is located in the bonnet locking platform. The top hose from the radiator is connected to the temperature sensor housing and bottom hose is connected, via a pipe, to the thermostat housing.

For additional air flow through the radiator matrix, particularly when the vehicle is stationary, an electric cooling fan is fitted to the rear of the radiator. The temperature of the cooling system is monitored by the Engine Control Module (ECM) via signals from a temperature sensor, which is mounted in a housing attached to the cylinder head. When a temperature of 102°C is reached the ECM switches the cooling fan on via a relay. The fan switches off at 96°C.

Vehicles fitted with air conditioning have 2 fans. These operate either in series or parallel according to engine coolant temperature or air conditioning requirements. The fan operation is controlled by the ECM. The fans operate in series (slow mode) when a temperature of 106°C or higher is sensed. When a temperature of 112°C is sensed, the fans switch from series to parallel operation (fast mode). When the temperature falls to 106°C or below, the fans are switched back to series operation. The fans stop when a temperature of 100°C or lower is sensed.

The cooling system is also used to cool the Intermediate Reduction Drive (IRD). The IRD oil is cooled with fluid from the cylinder block. The fluid passes through a plate which contains waterways and recirculates via the heater circuit.

Bleed screws are installed in the top hose of the heater matrix and the feed pipe to the coolant pump. These are used to bleed air from the cooling system during system filling.