Cooling system - K Series 1.8 (Description): Description and operation

Description

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 cooling system's primary function is to maintain the engine within an optimum temperature range under changing ambient and engine operating conditions. A secondary function of the cooling system is to provide additional cooling for the Intermediate Reduction Drive (IRD) and to provide heating for the passenger compartment.

The cooling system comprises: l A radiator l A passenger compartment heater matrix l An IRD cooler l A coolant pump l A thermostat l An expansion tank l One or two cooling fans l Connecting hoses and pipes.

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 an aluminium 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 the 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, one or two electric cooling fans are 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.

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 type heat exchanger located in the IRD. The plate which contains waterways which cool the IRD oil and recirculates the coolant 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.

The cooling system can have one or two cooling fans. Vehicles without air conditioning (A/C) have one cooling fan and vehicles with A/C have two cooling fans.

On vehicles without A/C, the single cooling fan is controlled by the ECM via a remote relay located in the E-box