OPERATION
Coolant flows through the engine block absorbing the heat from the engine, then flows to the radiator where the cooling fins in the radiator transfers the heat from the coolant to the atmosphere. During cold weather, the ethylene-glycol or propylene-glycol coolant prevents water present in the cooling system from freezing within temperatures indicated by mixture ratio of coolant to water.
DESCRIPTION
The coolant reserve/overflow tank is mounted on top of the fan shroud, and is made of high temperature plastic (Scheme 38)
Scheme 38
The coolant reserve/overflow system works in conjunction with the radiator pressure cap. It utilizes thermal expansion and contraction of coolant to keep coolant free of trapped air. It provides a volume for expansion and contraction of coolant. It also provides a convenient and safe method for checking coolant level and adjusting level at atmospheric pressure. This is done without removing the radiator pressure cap. The system also provides some reserve coolant to the radiator to cover minor leaks and evaporation or boiling losses.
As the engine cools, a vacuum is formed in the cooling system of both the radiator and engine. Coolant will then be drawn from the coolant tank and returned to a proper level in the radiator.
The coolant degas container is mounted on top of the fan shroud, and is made of high temperature plastic (Scheme 39)
Scheme 39
The coolant degas system works in parallel with the radiator. It is fed through a vent line connected to the top of the radiator inlet tank, and returns to the engine/coolant pump via the heater return hoses. This plumbing arrangement, together with the inlet thermostat, provides for constant flow through the degas container whenever the engine is running. The air space in the top of the degas container serves several functions. It provides a volume for the expansion of coolant during engine operation. It provides a space for quick de-aeration of the coolant. Since the container is the highest point in the cooling system, any air trapped in the coolant will quickly be transported to the degas container and be separated out.
The air space also acts as sort of a spring that provides constant system pressurization in conjunction with the radiator cap on top of the container. By returning coolant to the pump side of the inlet thermostat, the degas container also supplies greater pressure to the coolant pump, providing for enhanced coolant flow at high engine speeds.
The degas container also provides a convenient and safe method for checking the coolant level with out removing the radiator pressure cap. The degas container does not require a separate overflow container since it was designed with enough volume to provide a coolant reserve and also protect for any after-boil conditions.
| WARNING | DO NOT operate engine unless block heater cord has been disconnected from power source and secured in place. The power cord must be secured in its retaining clips, and routed away from exhaust manifolds and moving parts. |
An optional engine block heater is available with all models. The heater is equipped with a power cord. The cord is attached to an engine compartment component with tie-straps. The heater warms the engine providing easier engine starting and faster warm-up in low temperatures. The heater is mounted in a core hole of the engine cylinder block in place of a freeze plug with the heating element immersed in engine coolant. The 5.9L gas powered engine has the block heater located on the right side of engine next to the oil filter (Scheme 40) The 3.7L/4.7L gas powered engines have the block heater located to the rear on the right side of the engine (Scheme 41)
Scheme 40
Scheme 41
The heater warms the engine coolant providing easier engine starting and faster warm-up in low temperatures. Connecting the power cord to a grounded 110-120 volt AC electrical outlet with a grounded three wire extension cord provides the electricity needed to heat the element.
| WARNING | DO NOT operate engine unless block heater cord has been disconnected from power source and secured in place. The power cord must be secured in its retaining clips, and routed away from exhaust manifolds and moving parts. |
An optional engine block heater is available on all models. The heater is equipped with a power cord. The heater is mounted in a threaded hole of the engine cylinder block with the heating element immersed in engine coolant. The cord is attached to an engine compartment component with tie-straps.
The 5.9L diesel engine has the block heater located on the right side of the engine, below the exhaust manifold, next to the oil cooler (Scheme 42)
Scheme 42
The heater warms the engine coolant providing easier engine starting and faster warm-up in low temperatures. Connecting the power cord to a grounded 110-120 volt AC electrical outlet with a grounded three wire extension cord provides the electricity needed to heat the element.
Scheme 43
- Disconnect the battery negative cables.
- Drain coolant from radiator and cylinder block. Refer to «COOLING»(ref-189654-S13811322982005091200000).
- Unscrew the power cord retaining cap, and disconnect cord from heater element.
- Using a suitable size socket, loosen and remove the block heater element (Scheme 43)
The Engine Coolant Temperature (ECT) sensor is used to sense engine coolant temperature. The sensor protrudes into an engine water jacket.
The ECT sensor is a two-wire Negative Thermal Coefficient (NTC) sensor. Meaning, as engine coolant temperature increases, resistance (voltage) in the sensor decreases. As temperature decreases, resistance (voltage) in the sensor increases.
At key-on, the Powertrain Control Module (PCM) sends out a regulated 5 volt signal to the ECT sensor. The PCM then monitors the signal as it passes through the ECT sensor to the sensor ground (sensor return).
When the engine is cold, the PCM will operate in Open Loop cycle. It will demand slightly richer airfuel mixtures and higher idle speeds. This is done until normal operating temperatures are reached.
The PCM uses inputs from the ECT sensor for the following calculations
- For engine coolant temperature gauge operation through CCD or PCI (J1850) communications.
- Injector pulse-width.
- Spark-advance curves.
- ASD relay shut-down times.
- Idle Air Control (IAC) motor key-on steps.
- Pulse-width prime-shot during cranking.
- O2 sensor closed loop times.
- Purge solenoid on/off times.
- EGR solenoid on/off times (if equipped).
- Leak Detection Pump operation (if equipped).
- Radiator fan relay on/off times (if equipped).
- Target idle speed.
| CAUTION | Do not operate an engine without a thermostat, except for servicing or testing. |
The thermostat on the 5.7L and 5.9L gas powered engine is located beneath the thermostat housing at the front of the intake manifold see scheme 24
The thermostat is a wax pellet driven, reverse poppet choke type.
Coolant leakage into the pellet container will cause the thermostat to fail in the open position. Thermostats very rarely stick. Do not attempt to free a thermostat with a prying device.
The same thermostat is used for winter and summer seasons. An engine should not be operated without a thermostat, except for servicing or testing. Operating without a thermostat causes longer engine warm-up time, unreliable warm-up performance, increased exhaust emissions and crankcase condensation that can result in sludge formation.
Scheme 44
The wax pellet is located in a sealed container at the spring end of the thermostat. When heated, the pellet expands, overcoming closing spring tension and water pump pressure to force the valve to open.
| CAUTION | Do not operate the engine without a thermostat, except for servicing or testing. |
A pellet-type thermostat controls the operating temperature of the engine by controlling the amount of coolant flow to the radiator. On all engines, the thermostat is closed below 195°F (90°C). Above this temperature, coolant is allowed to flow to the radiator. This provides quick engine warm up and overall temperature control. On the 3.7L and 4.7L engines, the thermostat is designed to block the flow of the coolant bypass journal by 50% instead of completely blocking the flow. This design controls coolant temperature more accurately see scheme 31
The same thermostat is used for winter and summer seasons. An engine should not be operated without a thermostat, except for servicing or testing. Operating without a thermostat causes other problems. These are: longer engine warm-up time, unreliable warm-up performance, increased exhaust emissions and crankcase condensation. This condensation can result in sludge formation.
Scheme 45
The wax pellet is located in a sealed container at the spring end of the thermostat. When heated, the pellet expands, overcoming closing spring tension and water pump pressure to force the valve to open.
| CAUTION | Do not operate an engine without a thermostat, except for servicing or testing. An engine with the thermostat removed will operate in the radiator by-pass mode, causing an overheat condition. |
The thermostat of the 5.9L diesel engine is located in the front of the cylinder head, underneath the thermostat housing (Scheme 48)
The same thermostat is used for winter and summer seasons. An engine should not be operated without a thermostat, except for servicing or testing. Operating without a thermostat will cause overheating.
Scheme 46
The wax pellet is located in a sealed container at the spring end of the thermostat. When heated, the pellet expands, overcoming closing spring tension and water pump pressure to force the valve to open.
| CAUTION | DO NOT operate an engine without a thermostat, except for servicing or testing. |
The thermostat on all gas powered engines is located beneath the thermostat housing at the front of the intake manifold (Scheme 50)
Scheme 47
The thermostat is a moveable sleeve type.
Coolant leakage into the pellet container will cause the thermostat to fail in the open position. Thermostats very rarely stick. DO NOT attempt to free a thermostat with a prying device.
The same thermostat is used for winter and summer seasons. An engine should not be operated without a thermostat, except for servicing or testing. Operating without a thermostat causes longer engine warm-up time, unreliable warm-up performance, increased exhaust emissions and crankcase condensation that can result in sludge formation.
The wax pellet is located in a sealed container at the spring end of the thermostat. When heated, the pellet expands, overcoming closing spring tension and water pump pressure to force the valve to open.
The thermal viscous fan drive (Scheme 53) is a silicone fluid-filled coupling used to connect the fan blades to the water pump shaft. The coupling allows the fan to be driven in a normal manner. This is done at low engine speeds while limiting the top speed of the fan to a predetermined maximum level at higher engine speeds.
Scheme 48
A thermostatic bimetallic spring coil is located on the front face of the viscous fan drive unit (a typical viscous unit is see scheme 40). This spring coil reacts to the temperature of the radiator discharge air. It engages the viscous fan drive for higher fan speed if the air temperature from the radiator rises above a certain point. Until additional engine cooling is necessary, the fan will remain at a reduced RPM regardless of engine speed.
Only when sufficient heat is present, will the viscous fan drive engage. This is when the air flowing through the radiator core causes a reaction to the bimetallic coil. It then increases fan speed to provide the necessary additional engine cooling.
Once the engine has cooled, the radiator discharge temperature will drop. The bimetallic coil again reacts and the fan speed is reduced to the previous disengaged speed.
Scheme 49
The electronically controlled thermal viscous fan drive see scheme 41 is attached to the fan drive pulley mounted to the engine. The coupling allows the fan to be driven in a normal manner. The fan speed is controlled by the electronic control module.
Scheme 50
The Engine Control Module (ECM) controls the level of engagement of the electronically controlled viscous fan clutch by monitoring coolant temperature, intake manifold temperature, and air conditioning status. Based on cooling requirements, the ECM sends a signal to the viscous fan clutch to increase or decrease the fan speed.
Fan speed is monitored by the ECM. A lack of fan speed will set a DTC. Circuit concerns will also set fan clutch DTCs.
Fan speed and duty cycle percent can be monitored with the DRB III.
The radiator is a aluminum cross-flow design with horizontal tubes through the radiator core and vertical plastic side tanks (Scheme 54)
This radiator does not contain an internal transmission oil cooler
Scheme 51
The radiator supplies sufficient heat transfer using the cooling fins interlaced between the horizontal tubes in the radiator core to cool the engine.
The radiator is a aluminum cross-flow design with horizontal tubes through the radiator core and vertical plastic side tanks see scheme 45
This radiator does not contain an internal transmission oil cooler.
Scheme 52
The radiator supplies sufficient heat transfer using the cooling fins interlaced between the horizontal tubes in the radiator core to cool the engine.
All cooling systems are equipped with a pressure cap (Scheme 56) For 5.9L engines, the pressure cap is located on top of the radiator outlet tank. For the 3.7L/4.7L engines, the pressure cap is located on top of the coolant degas container. The cap releases pressure at some point within a range of 97-to-124 kPa (14-to-18 psi). The pressure relief point (in pounds) is engraved on top of the cap.
The cooling system will operate at pressures slightly above atmospheric pressure. This results in a higher coolant boiling point allowing increased radiator cooling capacity. The cap contains a springloaded pressure relief valve. This valve opens when system pressure reaches the release range of 97-to-124 kPa (14-to-18 psi).
A rubber gasket seals the radiator filler neck. This is done to maintain vacuum during coolant cool-down and to prevent leakage when system is under pressure.
Scheme 53
A vent valve in the center of the cap will remain shut as long as the cooling system is pressurized. As the coolant cools, it contracts and creates a vacuum in the cooling system. This causes the vacuum valve to open and coolant in the reserve/overflow container to be drawn through the recovery hose connecting the filler neck and reserve/overflow container. If the vacuum valve is stuck shut, or the recovery hose is kinked, radiator hoses will collapse on cool-down.
For the 3.7L/4.7L engines, the vacuum valve will open and relieve the vacuum pressure in the cooling system.
The water pump is located on the engine front cover, and has an integral pulley attached see scheme 50
The water pump impeller is pressed onto the rear of a shaft that rotates in a bearing pressed into the water pump body. The body has a small hole for ventilation. The water pump seals are lubricated by antifreeze in the coolant mixture. Additional lubrication is not necessary.
Scheme 54
A centrifugal water pump circulates coolant through the water jackets, passages, intake manifold, radiator core, cooling system hoses and heater core. This coolant absorbs the heat generated when the engine is running. The pump is driven by the engine crankshaft via a drive belt.
DESCRIPTION - WATER PUMP
A centrifugal water pump circulates coolant through the water jackets, passages, intake manifold, radiator core, cooling system hoses and heater core. The pump is driven from the engine crankshaft by a single serpentine drive belt.
The water pump impeller is pressed onto the rear of a shaft that rotates in bearings pressed into the housing. The housing has two small holes to allow seepage to escape. The water pump seals are lubricated by the antifreeze in the coolant mixture. No additional lubrication is necessary.
Both heater hoses are connected to fittings on the timing chain front cover. The water pump is also mounted directly to the timing chain cover and is equipped with a non-serviceable integral pulley see scheme 54
Scheme 55
DESCRIPTION - WATER PUMP BYPASS
The 3.7L and 4.7L engine uses an internal water/coolant bypass system. The design uses galleries in the timing chain cover to circulate coolant during engine warm-up preventing the coolant from flowing through the radiator. The thermostat uses a stub shaft located at the rear of the thermostat see scheme 55 to control flow through the bypass gallery.
Scheme 56
OPERATION - WATER PUMP
A centrifugal water pump circulates coolant through the water jackets, passages, intake manifold, radiator core, cooling system hoses and heater core. This coolant absorbs the heat generated when the engine is running. The pump is driven by the engine crankshaft via a drive belt.
OPERATION - WATER PUMP BYPASS
When the thermostat is in the closed position, the bypass gallery is not obstructed, allowing 100% flow. When the thermostat is in the open position, the stub shaft enters the bypass gallery, obstructing bypass coolant flow by 50%. This design allows the coolant to reach operating temperature quickly when cold, while adding extra cooling during normal temperature operation.
The water pump is mounted to the front of the engine block between the automatic belt tensioner and the fan drive pulley.
The water pump impeller is pressed onto the rear of a shaft that rotates in a bearing pressed into the water pump body. The body has a small hole for ventilation. The water pump seals are lubricated by antifreeze in the coolant mixture. Additional lubrication is not necessary.
The diesel engine water pump draws coolant from radiator outlet and circulates it through engine, heater core and back to radiator inlet. The crankshaft pulley drives the water pump with a serpentine drive belt.