The cooling system is of the pressurised pump-assisted thermo-syphon type. The system consists of the radiator, water pump, thermostat, electric cooling fan, expansion tank and associated hoses.

The system functions as follows. When the coolant is cold the thermostat is shut and coolant flow is restricted to the cylinder block, cylinder head, inlet manifold and the vehicle interior heater matrix. As the temperature of the coolant rises, the thermostat opens allowing the coolant to pass into the radiator.

The coolant now circulates through the radiator where it is cooled by the inrush of air when the car is in forward motion, supplemented by the operation of the radiator cooling fan. Coolant is then circulated from the base of the radiator, up through the water pump, and into the cylinder block to complete the circuit.

On OHV engines, the water pump is driven by a vee-belt from the crankshaft pulley. On CVH engines, the water pump is driven by the timing belt.

When the engine is at normal operating temperature the coolant expands, and some of it is displaced into the expansion tank. The coolant collects in the tank and is returned to the radiator when the system cools. On 1.1 litre engines the system pressure cap is fitted to the thermostat housing and the expansion tank acts as a simple overflow bottle. On all other engines the pressure cap is fitted to the expansion tank which is pressurised with the rest of the system.

On all engines except 1.1 litre CVH versions the radiator cooling fan is controlled by a thermal switch located in the thermostat housing. When the coolant reaches a predetermined temperature the switch contacts close thus actuating the fan. On 1.1 litre CVH engines with standard equipment the cooling fan operates continuously whenever the ignition is switched on.