Description And Operation: Description
COOLANT PUMP
| ITEM | DESCRIPTION |
|---|---|
| 1 | Inlet connection |
| 2 | Coolant pump body |
| 3 | Outlet flange to Bank 1 cylinder head |
| 4 | Outlet to engine oil cooler |
| 5 | Outlet flange to Bank 2 cylinder head |
| 6 | Pulley |
| 7 | Bleed pipe connection (containing check valve) |
The body of the coolant pump contains an impeller attached to a shaft supported in a bearing assembly. The impeller is driven by a pulley, pressed on to the front of the shaft, which is driven by the accessory drive belt.
For additional information, Refer to: Accessory Drive
Two coolant outlet flanges attach the coolant pump to the front of the cylinder block. A pipe connects a further coolant outlet to a pipe from the engine oil cooler. A bleed connector is installed in the front of the coolant pump, adjacent to the coolant inlet connection from the thermostat. A check valve is incorporated into the bleed connection.
ELECTRIC THERMOSTAT
| ITEM | DESCRIPTION |
|---|---|
| 1 | Coolant pump connection |
| 2 | Engine coolant outlet tube connection |
| 3 | Heater element electrical connector |
| 4 | Radiator lower hose connection |
| 5 | Coolant expansion tank connection |
The electric thermostat is a multi-stage device located in the coolant pump inlet to provide fast response and control of the engine outlet temperature.
The electric thermostat has 4 connections. The lower connection receives a quick fit connector which receives coolant from the radiator lower hose and the ATF cooler. The larger upper connection is connected via a hose, water supply tube and water outlet to the cylinder block. The flow from this connection is governed by the thermostat. A connection at the side provides flow to the coolant pump and a smaller connection from this receives coolant return from the heater core and the coolant expansion tank.
The thermostat allows rapid engine warm-up by preventing coolant flow through the radiator and by limiting coolant flow through the cylinder block when the engine is cold. During warm-up and at engines speeds above approximately 1800 RPM, a by-pass valve opens to control the coolant flow and pressure, to protect the engine components. When the thermostat opening reaches 6 mm (0.24 in.), the by-pass flow is shut-off. When the thermostat opening exceeds 6 mm (0.24 in.), the radiator coolant flow is further controlled up to the point where the thermostat is fully open. At this point maximum radiator coolant flow is achieved to provide maximum cooling.
The thermostat begins to open (with ambient temperatures of 15-35°C (59-95 °F)) at 98-102 °C (208-215 °F) and is fully open at 108 °C (226 °F).
The electrically heated thermostat is used to regulate the engine coolant temperature by the ECM. The increased wax temperature provides higher coolant temperature during part load conditions and at low speed cycles. The increased coolant temperature results reduced friction in the engine, improved combustion in the cylinders, and reduced fuel consumption and emissions. An electric thermostat heater element assembled within the wax element to regulate the engine coolant temperature during high load conditions and speed points to protect the engine from thermal overload.
Operation of the electric thermostat is controlled by the ECM upon the following inputs:
- Engine load
- Engine speed
- Vehicle speed
- Coolant temperature
- Terrain response inputs
- ATF temperature
The electric thermostat has a switched power supply from the ECM relay, located in the EJB and a hardwired connection to the ECM. If the ECM starts to regulate the system, the ECM supplies a ground path for the heater element in the electric thermostat. This causes the element to expand and increase the opening dimension of the thermostat.
RADIATOR
| ITEM | DESCRIPTION |
|---|---|
| 1 | Bleed hose connection |
| 2 | Upper hose connection |
| 3 | Automatic Transmission Fluid (ATF) cooler supply hose connection |
| 4 | Lower hose connection |
| 5 | Radiator lower support (2 off) |
| 6 | Radiator upper support (2 off) |
The radiator is an aluminum cross flow type with plastic end tanks. Upper and lower supports locate the radiator in the radiator support assembly and the front crush side rails respectively.
Connections are incorporated into the end tanks for the upper and lower hoses, the supply hose of the ATF cooler and a bleed hose.
VISCOUS COOLING FAN
| ITEM | DESCRIPTION |
|---|---|
| 1 | Securing nut |
| 2 | Harness |
| 3 | Electro-viscous drive unit |
For additional airflow through the radiator, particularly when the vehicle is stationary or moving slowly, there is an engine driven electro-viscous cooling fan. The cooling fan functions as a normal viscous fan, but with electronic control over the level of engagement of the viscous clutch. The ECM controls the level of engagement to optimize fan speed for all operating conditions.
A securing nut attaches the cooling fan to a drive pulley, which is mounted on the front of the engine and driven by the accessory drive system.
For additional information, Refer to: Accessory Drive
The blades of the cooling fan are located in a fan cowl attached to the rear of the radiator frame. Brushes around the circumference of the aperture in the fan cowl provide a seal with the blade shroud. An electrical connector in the top left corner of the fan cowl provides the interface between the cooling fan harness and the vehicle wiring.
The viscous cooling fan is operated by the VCFCM (Viscous Cooling Fan Control Module), integrated into the drive unit, which is controlled by the ECM. An electrical connector in the top right corner of the fan cowl provides the interface between the cooling fan harness and the vehicle wiring.
The control module is provided with:
- Two battery power supplies from the ECM relay in the EJB (Engine Junction Box)
- A PWM (Pulse Width Modulation) signal from the ECM
- A ground
A Hall effect sensor in the VCFCM provides a fan speed signal for the ECM. To control the cooling fan speed, the ECM varies the duty cycle of the PWM signal. The VCFCM translates the duty cycle into a fan target speed and sets the level of engagement of the viscous clutch accordingly.
EXPANSION TANK
| ITEM | DESCRIPTION |
|---|---|
| 1 | Filler cap |
| 2 | MAX and MIN level markings |
| 3 | Mounting lug |
| 4 | Supply hose connection |
| 5 | Coolant level sensor |
| 6 | Mounting lugs |
| 7 | Bleed screw |
| 8 | Vent hose connection |
A pressurized expansion tank system is used which continuously separates the air from the cooling system and replenishes the system through a hose connected between the expansion tank and the thermostat. A continuous vent into the expansion tank, through a hose connected to the radiator, prevents air locks from forming in the cooling system.
The expansion tank is attached to the front end carrier in the front left corner of the engine compartment. A filler cap, bleed screw and level sensor are incorporated into the expansion tank. MAX and MIN level markings are molded into the exterior of the tank.
The expansion tank provides the following functions:
- Service fill.
- Coolant expansion during warm-up.
- Air separation during operation.
- System pressurization by the filler cap.
The expansion tank has an air space of approximately 0.5 to 1 liter (1.06 to 2, 11 US pints), above the MAX level, to allow for coolant expansion.
OUTLET TUBE AND HEATER MANIFOLD
Outlet Tube
| ITEM | DESCRIPTION |
|---|---|
| 1 | Bleed spigot (fitted with blanking plug) |
| 2 | Radiator upper hose connection |
| 3 | Cylinder block connections |
| 4 | Thermostat hose connection |
Heater Manifold
| ITEM | DESCRIPTION |
|---|---|
| 1 | Electric throttle heater Hose connection |
| 2 | Heater core supply hose connection |
| 3 | Cylinder head connection - Bank 1 |
| 4 | Engine Coolant Temperature (ECT) sensor 1 |
| 5 | Cylinder head connection - Bank 2 |
ENGINE COOLANT
The engine coolant is formulated to last for ten years or 240, 000 km (150, 000 miles). The coolant is silicate free and must not be mixed with conventional engine coolant.