Coolant System
COOLING SYSTEM DESCRIPTION
Major Components
- Main engine crossflow radiator, incorporating a concentric tube cooler for the power steering fluid mounted in the right-hand radiator side tank. Vehicles with automatic transmission have a transmission fluid cooler mounted in the left-hand radiator side tank; for 4.0 liter supercharged engines a six-plate cooler is fitted; other vehicles have a tube-type cooler. A double-action temperature switch, for controlling the radiator cooling fans, is mounted in the left-hand radiator side tank.
- Two electrically operated radiator cooling fans, mounted behind the main radiator.
- Coolant circulating pump, belt driven from the engine crankshaft.
- Coolant header tank with pressure relief cap and coolant level probe.
- Engine thermostat.
Components for Climate Control System
- Heater matrix.
- Electrically operated coolant circulating pump, mounted on the left-hand side of the engine bulkhead.
- Solenoid operated valve, located adjacent to the coolant circulating pump.
Components for Supercharged Engine
- Supercharger crossflow radiator, mounted in front of the main radiator. The supercharger radiator is reverse-circuited, i.e. the coolant inlet is at the bottom of the radiator.
- Electrically operated coolant circulating pump, located at the left-hand side of the main radiator.
Operation
The configuration of the cooling system for normally aspirated and supercharged (4.0 liter) engines is shown in System Configuration.
The cooling system is pressurized, which allows the system to operate at a higher temperature without overheating. The header tank is fitted with a pressure relief cap to protect the system against overpressure.
Under cold start conditions, coolant is forced by the engine driven coolant pump through the cylinder block and cylinder head to the thermostat housing. The thermostat is closed to give rapid engine warm up, hence the coolant is returned directly to the coolant pump inlet. When normal engine operating temperature is reached, the thermostat opens and coolant is diverted through the radiator before returning to the coolant pump inlet. In vehicles fitted with a supercharger, coolant is circulated through the supercharger radiator and intercooler by the supercharger coolant pump. The supercharger cooling circuit uses the same coolant header tank as the main engine cooling system.
The radiator cooling fans operate in series and parallel under the control of the double-action radiator mounted temperature switch. The fans are also controlled by the climate control system on vehicles fitted with air conditioning. Under hot operating conditions, the fans may continue to operate after the engine has been switched off. The fans stop automatically when the coolant temperature has been reduced sufficiently.
The system also provides the coolant supply for the climate control system, which is described in Heating and Air Conditioning.
Updates: Cooling System
Engine Cooling System
Changes to the cooling system consist of a new radiator, coolant reservoir, engine-driven coolant pump and radiator bottom hose. In addition, a new shut-off valve and an electric pump are introduced to the heater circuit. On vehicles with the SC engine, a new coolant circuit is introduced for the supercharger intercooler. The intercooler circuit contains a radiator and an electric pump, together with the necessary connecting hoses.
The cooling system has also been improved by reducing the number of inlets to the coolant pump and the number of connections.
Radiator
The new radiator is thinner and lighter than the previous version, but retains the same performance. Core depth is reduced from 40 mm (1.57 in) to 32 mm (1.26 in). On vehicles with a SC engine, the left side of the radiator incorporates a six plate cooler for transmission fluid.
Coolant Reservoir
The new coolant reservoir is introduced to accommodate changes to the body. The coolant level probe is installed in the base of the reservoir. A connector on the base of the probe provides the interface with the vehicle harness.
Engine-driven Coolant Pump
A new coolant pump, with only one intake connection, is installed. The intake connections from the filler pipe and the thermostat housing are deleted, leaving the radiator bottom hose as the only intake connection.
With the introduction of the electric air injection pump the drive belt between the coolant pump and the air injection pump is deleted. A single groove pulley replaces the previous twin groove pulley. The capacity of the pump is unchanged.
Heater Shut-off Valve
The solenoid operated shut-off valve is installed in the engine compartment, on the left side of the toe-board. The shut-off valve simultaneously opens or closes the supply and return lines of the heater, under the control of the climate or heater control modules (see Heating and Air Conditioning for details).
Heater Pump
The electric heater pump is installed on the toeboard, adjacent to the heater shut-off valve, in the supply line to the heater. Operation of the pump is also controlled by the climate or heater control modules.
Fill Pipe
The fill pipe now connects to the radiator bottom hose.
Radiator Bottom Hose
The radiator bottom hose is revised to accommodate the new coolant pump. In addition, the hoses from the thermostat housing bypass, heater outlet and throttle body outlet are now integrated into the bottom hose.
Supercharger Radiator
The supercharger radiator is a fin and tube, liquid to air heat exchanger installed between the air conditioning condenser and the front grille.
Supercharger Coolant Pump
The supercharger coolant pump is an electric pump used to ensure an adequate flow of coolant through the intercooler. It is attached to the left end of the cross tube, adjacent to the air cleaner, in the return line from the intercooler. The pump runs continuously while the ignition is switched on.
Supercharger Coolant Hoses
Additional hoses are introduced to form the supercharger coolant circuit. A connection on the hose between the intercooler and the supercharger coolant pump is attached to the radiator bottom hose, to provide an interface with the engine coolant circuit. To accommodate the connection of the intercooler bleed hose with the coolant reservoir, the bleed hoses from the engine thermostat housing and the main radiator are connected to the coolant reservoir via a Tee connector.