Cooling System: Description and Operation
Engine Cooling - Vehicles Without: SuperchargerCOMPONENT LOCATION
INTRODUCTION
WARNING: Never remove the coolant pressure cap under any circumstances while the engine is operating. Failure to follow this instruction may result in personal injury. To avoid having scalding hot coolant or steam blow out of the cooling system, use extreme care when removing the coolant pressure cap from a hot cooling system. Wait until the engine has cooled, then wrap a thick cloth around the coolant pressure cap and turn it slowly until the pressure begins to release. Step back while the pressure is released from the system. When certain all the pressure has been released turn and remove the coolant pressure cap (still with a cloth) from the coolant expansion tank. Failure to follow these instructions may result in personal injury.
WARNING: To avoid the possibility of personal injury, do not operate the engine with the hood open until the fan blades have been examined for cracks and separation. Failure to follow this instruction may result in personal injury.
WARNING: Remove fuse 38 from the Battery Junction Box (BJB) prior to performing any under hood service in the area of the cooling fan when the engine is hot, since the cooling fan motor could operate if the engine has been switched OFF. Failure to follow this instruction may result in personal injury.
CAUTION: The engine cooling system must be maintained with the correct concentration and type of antifreeze solution to prevent corrosion and frost damage.
CAUTION: Never remove the coolant pressure cap under any circumstances while the engine is operating. Failure to follow this instruction may result in damage to the engine.
Engine cooling is via a low volume, high velocity system, which achieves a very fast warm up. The temperature of the combustion chambers is reduced along with a more even temperature distribution.
The coolant expansion tank has an integral bleed screw and coolant-level sensor. The auxiliary coolant-flow pump is fitted as standard.
The cooling-fan speed is controlled directly by the Engine Control Module (ECM) based on input data measured by the Engine Coolant Temperature (ECT) sensor, the climate control pressure-transducer and the transmission oil temperature sensor. The ECM processes this input data and outputs a Pulse Width Modulated (PWM) signal, which determines the fan speed. Should the output signal fall outside predetermined parameters, maximum fan-speed is initiated to protect the engine. High engine temperature is indicated by the illumination of the engine over-temperature warning light, located in the instrument cluster.
Where appropriate, to provide an extended period of engine cooling, the ECM continues to control the fan speed after the ignition has been turned off.
A coolant drain plug is located at the rear of the cylinder block behind the starter motor.
COOLANT PUMP
The coolant pump is fitted between the 2 cylinder banks, on the front face of the cylinder block.
The pump consists of a housing containing a shaft, with a shrouded plastic impeller on one end and a drive pulley on the other.
A pair of roller bearings supports the shaft in the housing. A seal behind the impeller prevents coolant from contaminating the bearings. Should this seal fail, coolant escapes from a witness hole in the housing indicating that immediate action is required.
An O-ring and an aluminum-alloy gasket, seal the ports between the pump and the cylinder banks.
From the pump, coolant flows into each bank of the cylinder block. In each bank, approximately 50% of the coolant cools the cylinder bores and the remainder is diverted through the bypass gallery to the cylinder head.
With the thermostat closed, coolant returns directly to the pump through the bypass on the thermostat housing.
With the thermostat open, coolant returns to the pump via the radiator.
COOLANT OUTLET ASSEMBLY
A coolant outlet plastic pipe connects to the outlet port of each cylinder head to provide a common connection point for the radiator top hose. It also incorporates the ECT sensor, which provides a signal representing coolant temperature at the cylinder heads. Controlling the coolant flow through the radiator, the thermostat starts to open at 80 degrees C (176 degrees F) to 84 degrees C (183 degrees F) and is fully open at 96 degrees C (205 degrees F). The outlet pipe has connections to supply the heater core and the bypass flow to the thermostat housing. An in-groove gasket seals each of the outlet-to-cylinder head joints. An aluminium gasket seals the ECT sensor to thermostat housing.
RADIATOR
The cooling pack incorporates the radiator assembly with integral transmission oil cooler (located in the radiator outlet tank), an air conditioning condenser, and the twin fan and motor assembly.
The radiator is mounted on 4 rubber mounts, one on each end of the upper and lower face. A closing panel, which retains the radiator assembly, fits over the top of the radiator and is secured to the vehicle body.
COOLING FANS
The 2 radiator cooling fans are mounted in a twin fan and motor assembly between the radiator and the engine.
The fan control module controls the fans dependent on the demand from the cooling system (temperature) or the air conditioning system (pressure).
The fan control module is located on the twin fan and motor shroud. The variable PWM module controls the fan speeds.
Under hot operating conditions, the fans may continue to operate for some time after the engine has been switched off, but will stop automatically when the coolant temperature has been sufficiently reduced.
ENGINE BLOCK HEATER
For vehicle markets subject to very cold climate conditions, an engine block heater for connection to an external mains power supply, is fitted in place of the engine block drain plug.
ENGINE OIL COOLER
The engine oil cooler is a Modine oil to water type. The oil cooler is located at the front of the engine and is fitted between the oil filter housing and the oil filter.
The coolant supply for the engine oil cooler is through the radiator bottom hose.
COOLANT RECOVERY SYSTEM
A pressurized coolant expansion tank system is used which continuously separates the air from the cooling system and replenishes the system through the coolant expansion tank outlet hose, attached to the heater return hose.
A continuous vent from the engine and radiator to the coolant expansion tank prevents air locks from forming in the cooling system.
Manual bleed points are provided on the coolant reservoir.
The coolant expansion tank serves as the location for:
^ Service fill
^ Coolant expansion during warm-up
^ Air separation during operation
^ System pressurization by the coolant pressure cap
^ The coolant expansion tank is designed to have approximately 0.5 to 1 liter of air when cold to allow for coolant expansion
ENGINE COOLANT TEMPERATURE (ECT) SENSOR
The ECT sensor is located in the coolant outlet pipe and reacts to engine coolant temperature changes, providing an input to the ECM. The sensor is a Negative Temperature Coefficient (NTC) thermistor, decreasing in resistance as the temperature rises.
ENGINE COOLANT
The long life engine coolant is formulated to last for 5 years or 240,000 km (150,000 miles). The coolant is silicate free and orange in color. The long life engine coolant must not be mixed with conventional engine coolant.
COOLANT FLOW
