Engine Cooling - Description

ENGINE COOLING - DESCRIPTION
General
The complete cooling system installed in vehicles with V8 engines incorporates three independent functions: Engine (coolant) cooling; Engine oil cooling; Gearbox oil cooling.

Engine and gearbox oil coolers are mounted in front of the radiator and linked to their separate systems by pre-formed pipes and hoses.

The cooling system used on the V8 engine is a pressurized, by-pass type system, which allows coolant to circulate around the engine block and heater matrix when the thermostat is closed. With coolant not passing through the radiator, faster heater warm-up is promoted which in turn improves passenger comfort.

A coolant pump is located in a housing at the front of the engine and is driven by a drive belt. The water pump is connected into the coolant passages cast into the cylinder block and pumps coolant from the radiator through the cylinder block and heater circuit.

A viscous fan is attached to the water pump drive pulley. The fan is secured by a left hand threaded nut to the pulley spindle. The fan draws air through the radiator to assist in cooling when the vehicle is stationary. The fan rotational speed is controlled relative to the running temperature of the engine by a thermostatic valve regulated by a bi-metallic coil.

The cooling system uses a 50/50 mix of anti-freeze and water.


Thermostat housing
A 'four way' thermostat housing, located at the bottom of the fan cowling behind the radiator, is used to link the main components within the engine cooling system. The four connections locate the radiator bottom hose, top hose, by-pass hose and coolant pump feed hose.

The plastic housing contains a wax element thermostat. The thermostat and housing are a sealed unit and cannot be replaced individually. The thermostat is used to maintain the coolant at the optimum temperature for efficient combustion and to aid engine warm-up.

The thermostat is closed at temperatures below approximately 80°C (176°F). When the coolant temperature reaches between 80 to 84°C (176 to 183°F) the thermostat starts to open and is fully open at approximately 96°C (204°F). In this condition the full flow of coolant is directed through the radiator.


Inlet manifold cooling connections
With the thermostat open, coolant leaves the cylinder block via an outlet pipe and top hose attached to the front of the inlet manifold. The top hose is connected to the top of the radiator.

Hot coolant from the cylinder block is also directed from the inlet manifold via pipes and hoses to the heater matrix. Coolant is circulated through the heater matrix at all times when the engine is running.


Plenum chamber- up to 99MY
The plenum chamber is heated with a supply of coolant from a supply pipe from the inlet manifold to a plate on the underside of the throttle on the plenum. The hot coolant prevents the air intake and throttle linkage from icing. A bleed pipe returns coolant from the plenum chamber to the expansion tank.


Throttle housing - from 99MY
A tapping from the inlet manifold supplies coolant to the throttle housing via a hose. The coolant circulates through a plate attached to the bottom of the throttle housing and is returned through a plastic bleed pipe to the expansion tank. The hot coolant heats the throttle housing preventing ice from forming.


ECT sensor and temperature gauge sender unit -up to 99MY
An Engine Coolant Temperature (ECT) sensor and a temperature gauge sender unit are located on the inlet manifold adjacent to the outlet pipe. The ECT sensor monitors coolant temperature emerging from the engine and sends signals relating to coolant temperature to the ECM for engine management. The temperature gauge sender unit operates the warning lamp and temperature gauge in the instrument pack.


ECT sensor - from 99MY
An Engine Coolant Temperature (ECT) sensor is located on the inlet manifold adjacent to the outlet pipe. The ECT sensor monitors coolant temperature emerging from the engine and sends signals relating to coolant temperature to the ECM for engine management and to the instrument pack for temperature gauge operation.


Expansion tank
The expansion tank is located in the engine compartment and attached to the right hand inner wing. The tank is made from molded plastic and has a maximum coolant level when cold mark molded on the side.

Excess coolant created by heat expansion is returned to the expansion tank from the bleed pipe at the top of the radiator. An outlet pipe is connected into the thermostat housing and replaces coolant displaced by heat expansion into the system when the engine is cool.

The tank is fitted with a sealed pressure cap. The cap contains a pressure relief valve, which opens to allow excessive pressure and coolant to vent through the overflow pipe. The relief valve opens at a pressure of 1.4 bar (20 inch lbs.) and above.


Heater matrix
The heater matrix is fitted in the distribution unit of the heating and ventilation system inside the passenger compartment. Two pipes pass through the bulkhead and provide coolant flow to and from the matrix.

The matrix is constructed from aluminum with two end tanks interconnected with tubes. Aluminum fins are located between the tubes and conduct heat away from the hot coolant flowing through the tubes. Air from the heater assembly is warmed as it passes through the matrix fins. The warm air is then distributed into the passenger compartment as required.


Radiator
The radiator is located at the front of the vehicle. The vertical flow radiator is manufactured from aluminum with molded plastic tanks at the top and bottom, interconnected with tubes. Aluminum fins are located between the tubes and conduct heat from the hot coolant flowing through the tubes, reducing the coolant temperature as it passes through the radiator. Air intake from the front of the vehicle when moving carries heat away from the fins. When the vehicle is stationary, the viscous fan draws air through the fins to prevent the engine from overheating.

Two connections at the top of the radiator provide for the attachment of the top hose and bleed pipe. A connection at the bottom of the radiator allows for the attachment of the bottom hose to the thermostat housing.

Two coolers are located in front of the cooling radiator. The upper cooler provides cooling of the engine oil and the lower cooler provides cooling for the gearbox oil.


Pipes and hoses
The coolant circuit comprises flexible hoses and metal formed pipes which direct coolant into and out of the engine, radiator and heater matrix. Plastic pipes are used for the bleed and overflow pipes to the expansion tank.

A drain plug is fitted to each cylinder bank in the cylinder block. These are used to drain the block of coolant.


Coolant pump





The coolant pump is attached to the front of the cylinder block with nine bolts and sealed between the pump housing and the cylinder block with a gasket. The pump comprises a shaft, which passes through an alloy housing.

The outer end of the shaft has a flange, which allows for the attachment of the pump drive pulley, which is secured with three bolts. The drive pulley is driven by the grooved auxiliary drive belt and rotates at the same speed as the crankshaft. The inner end of the shaft is fitted with an impeller, which draws coolant from the thermostat housing and circulates it through galleries in the cylinder block and through the heater matrix.

The shaft is supported on bearings in the housing which are packed with grease and sealed for life. A seal is positioned in the housing to further protect the bearings from the ingress of coolant. The seal is manufactured from a synthetic material, which will allow for the expansion of the casing when hot coolant is present.

The cast alloy housing has a hose connection, which provides the attachment for the coolant pump feed hose. The housing connects with galleries in the cylinder block and distributes coolant from the pump impeller into the galleries and water jackets.


Viscous fan





The viscous drive unit for the engine cooling fan provides a means of controlling the speed of the fan relative to the temperature of the engine. The viscous fan unit is a type of fluid coupling, which drives the fan blades by means of 'silicon fluid'.
1. Input (drive) member
2. Output (driven) member
3. Sensing mechanism (bi-metal coil)