Engine Cooling System: Overview Dodge Cab & Chassis R3500 HD

Scheme 8

The 3.7L/4.7L engine cooling system consists of

1. LH Cylinder Head (1)
2. Bleed (2)
3. Thermostat location (3)
4. RH Cylinder Head (4)
5. RH Bank Cyl. Block (5)
6. LH Bank Cyl. Block (6)
7. Coolant Temp Sensor (7)
8. From Heater Core (8)
9. To Heater Core (9)

The cooling system regulates engine operating temperature. It allows the engine to reach normal operating temperature as quickly as possible. It also maintains normal operating temperature and prevents overheating.

Scheme 9

The 5.7L engine cooling system consists of

1. LH Cylinder Head (1)
2. To Radiator (2)
3. From Radiator (3)
4. To RH Cylinder Head (4)

The cooling system provides a means of heating the passenger compartment and cooling the automatic transmission fluid (if equipped). The cooling system is pressurized and uses a centrifugal water pump to circulate coolant through the system. The coolant recovery/reserve system utilizes an ambient overflow bottle.

Scheme 10

The diesel engine cooling system consists of

1. Cross-flow radiator
2. Belt driven water pump
3. Belt driven Electronically Controlled Viscous fan drive (Diesel Engine)
4. Engine mounted fan shroud
5. Radiator pressure cap
6. Vertically mounted thermostat
7. Coolant reserve/recovery system
8. Transmission Oil Cooler (Automatic Transmission Only)
9. Engine mounted Transmission oil cooler
10. Radiator mounted fan shroud
11. EGR Cooler
12. Turbocharger Actuator

COOLING-OPERATION

The cooling system regulates engine operating temperature. It allows the engine to reach normal operating temperature as quickly as possible. It also maintains normal operating temperature and prevents overheating.

The cooling system also provides a source of hot coolant for heating the passenger compartment and cooling the automatic transmission fluid (if equipped). The cooling system is pressurized and uses a centrifugal water pump to circulate coolant throughout the system.

1. When engine is cold the thermostat is closed. The cooling system has no flow through the radiator. The coolant flows through the engine, water pump, and heater.
2. When engine is warm the thermostat is full open. One the gas engine coolant flows through the engine, radiator, heater, and water pump.
3. One the diesel engine coolant flows through the engine, radiator, EGR cooler, turbocharger actuator housing, heater, and water pump.

All engines utilize an ambient overflow bottle for coolant recovery/reserve.

An optional factory installed maximum duty cooling package is available on most models. This package will provide additional cooling capacity for vehicles used under extreme conditions such as trailer towing in high ambient temperatures.

Scheme 11

A leak detection additive is available through the parts department that can be added to cooling system. The additive is highly visible under ultraviolet light (black light) (1). Pour one ounce of additive into cooling system. Place heater control unit in HEAT position. Start and operate the engine until the radiator upper hose is warm to the touch. Aim the commercially available black light tool at the components to be checked. If leaks are present, the black light will cause the additive to glow a bright green color.

The black light can be used in conjunction with a pressure tester to determine if any external leaks exist.

DESCRIPTION

The accessory drive belt is a serpentine type belt. Satisfactory performance of these belts depends on belt condition and proper belt tension.

Correct drive belt tension is required to ensure optimum performance of the belt driven engine accessories. If specified tension is not maintained, belt slippage may cause; engine overheating, lack of power steering assist, loss of air conditioning capacity, reduced generator output rate, and greatly reduced belt life.

It is not necessary to adjust belt tension. All engines are equipped with an automatic belt tensioner. The tensioner maintains correct accessory drive belt tension at all times.

OPERATION

The automatic accessory drive belt tensioner maintains belt tension by using internal spring pressure, a pivoting arm and pulley to press against the drive belt.

Scheme 12

1. Remove accessory drive belt. See «REMOVAL»(ref-303804-S28153607332008103100000).
2. Remove tensioner (1) and mounting bracket.
3. Remove the tensioner assembly from the mounting bracket. (Scheme 12)

Scheme 13

On 3.7L and 4.7L engines, the tensioner is equipped with an indexing tang on back of tensioner and an indexing stop on tensioner housing. If a new belt is being installed, tang must be within approximately 24 mm (.94 inches) of indexing stop. Belt is considered new if it has been used 15 minutes or less.

If the above specification cannot be met, check for

1. The wrong belt being installed (incorrect length/width)
2. Worn bearings on an engine accessory (A/C compressor, power steering pump, water pump, idler pulley or generator)
3. A pulley on an engine accessory being loose
4. Misalignment of an engine accessory
5. Belt incorrectly routed.

Note. A used belt should be replaced if tensioner indexing arrow has moved to the minimum tension indicator. Tensioner travel stops at this point.

1. Remove accessory drive belt. See «REMOVAL»(ref-303804-S28153607332008103100000).
2. Remove tensioner (3) assembly from mounting bracket. (Scheme 13) WARNING: Because of high spring pressure, do not attempt to disassemble automatic tensioner. Unit is serviced as an assembly except for pulley on tensioner.
3. Remove pulley bolt. Remove pulley from tensioner.

Scheme 14

1. Remove accessory drive belt. See «REMOVAL»(ref-303804-S28153607332008103100000) .
2. Remove tensioner mounting bolt and remove tensioner (7).

COOLANT-DESCRIPTION-HOAT

The cooling system is designed around the coolant. The coolant must accept heat from engine metal, in the cylinder head area near the exhaust valves and engine block. Then coolant carries the heat to the radiator where the tube/fin radiator can transfer the heat to the air.

The use of aluminum cylinder blocks, cylinder heads, and water pumps requires special corrosion protection. Mopar® Antifreeze/Coolant, 5 Year/100,000 Mile Formula (MS-9769), or the equivalent ethylene-glycol base coolant with organic corrosion inhibitors (called HOAT, for Hybrid Organic Additive Technology) is recommended. This coolant offers the best engine cooling without corrosion when mixed with 50% ethylene-glycol and 50% distilled water to obtain a freeze point of -37°C (-35°F). If it loses color or becomes contaminated, drain, flush, and replace with fresh properly mixed coolant solution.

COOLANT-OPERATION

Coolant flows through the engine block, cylinder head, 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. On the 6.7L diesel engine, coolant also flows through the EGR cooler and turbocharger actuator. 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.

COOLANT RECOVERY CONTAINER-OPERATION

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.

Scheme 15

1. Disconnect washer pump electrical connector.
2. Remove recovery hose (3) from radiator (4).
3. Remove the coolant container to fan shroud mounting bolts (1).
4. Tilt the container (2) backward towards the engine to disengage the mounting pin locking features and lift the container away from the fan shroud (5).

Scheme 16

1. Remove overflow hose (5) from radiator (1)
2. Remove mounting bolts (4).
3. Remove coolant recovery bottle (2) from bracket (3).

ENGINE BLOCK HEATER-OPERATION

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.

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 air-fuel 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

1. for engine coolant temperature gauge operation through CAN Bus communications
2. Injector pulse-width
3. Spark-advance curves
4. ASD relay shut-down times
5. Idle Air Control (IAC) motor key-on steps
6. Pulse-width prime-shot during cranking
7. O2 sensor closed loop times
8. Purge solenoid on/off times
9. Cooling fan control
10. Temperature gauge operation
11. A/C cutoff at high coolant temperatures
12. EGR solenoid on/off times (if equipped)
13. Leak Detection Pump operation (if equipped)
14. Radiator fan relay on/off times (if equipped)
15. Target idle speed

Scheme 17

1. Partially drain the cooling system.
2. Disconnect the electrical connector from the ETC sensor (3).
3. Remove the sensor from the intake manifold (4).

Scheme 18

1. Partially drain the cooling system. See «STANDARD PROCEDURE»(ref-303804-S21721751352008103100000) .
2. Disconnect the electrical connector from the ECT sensor (1).
3. Remove the sensor from the intake manifold (4).

Scheme 19

1. Partially drain the cooling system. See «STANDARD PROCEDURE»(ref-303804-S21721751352008103100000).
2. Remove accessory drive belt. See «REMOVAL»(ref-303804-S28153607332008103100000).
3. Carefully unbolt air conditioning compressor from front of engine. Do not disconnect any A/C hoses from compressor. Refer to «REMOVAL»(ref-303776-S12199686782008103100000). Temporarily support compressor to gain access to ECT sensor (3).
4. Disconnect electrical connector from sensor. (Scheme 19)
5. Remove sensor from cylinder block.

Scheme 20

Scheme 21

1. Partially drain the cooling system. See «STANDARD PROCEDURE»(ref-303804-S21721751352008103100000) . 1 - THERMOSTAT HOUSING 2 - ELECTRICAL CONNECTOR 3 - ECT SENSOR
2. Remove heat shield (if equipped).
3. Disconnect the electrical connector (2) from the ETC sensor (3).
4. Remove the ETC sensor from the cylinder head.

The radiator supplies sufficient heat transfer using the cooling fins interlaced between the horizontal tubes in the radiator core to cool the engine.

OPERATION-3.7L/4.7/5.7L

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.

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.

Scheme 22

Remove the cap from the radiator. Be sure that the sealing surfaces are clean. Moisten the rubber gasket with water and install the cap on the pressure tester 7700 or an equivalent. (Scheme 22)

Operate the tester pump to bring the pressure to 104 kPa (15 psi) on the gauge. If the pressure cap fails to hold pressure of at least 97 kPa (14 psi) replace the cap. Refer to the following CAUTION .

The pressure cap may test properly while positioned on tool 7700 (or equivalent). It may not hold pressure or vacuum when installed on the radiator. If so, inspect the radiator filler neck and radiator cap's top gasket for damage. Also inspect for dirt or distortion that may prevent the cap from sealing properly.

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. see scheme 90

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-3.7L/4.7L

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 pill partially covers the bypass hole, reducing the amount of bypass flow. This design allows the coolant to reach operating temperature quickly when cold, while adding extra cooling during normal temperature operation.

The Exhaust Gas Recycling cooler is located above the exhaust manifold on the right side of the engine.

Exhaust gas enter the rear portion of the EGR Cooler from the exhaust manifold. The gas is cooled as it passes through the EGR Cooler and then enters the EGR crossover tube and is routed to the EGR valve.

Coolant enters the rear of the EGR Cooler and flow the same direction as the exhaust gases.

Scheme 23

Scheme 24

Scheme 25

Scheme 26

1. Remove engine cover (1).
2. Drain cooling system below level of EGR cooler. See «STANDARD PROCEDURE»(ref-303804-S21721751352008103100000) . 1 - EGR VALVE 2 - EGR HEAT SHIELD
3. Remove EGR heat shield. 1 - EGR COOLER TO CROSSOVER TUBE CLAMP 2 - EGR CROSSOVER TUBE 3 - EGR VALVE TO CROSSOVER TUBE CLAMP 4 - EGR VALVE TEMPERATURE SENSOR CONNECTOR 5 - CLAMP
4. Disconnect EGR temperature sensor electrical connector (4).
5. Loosen EGR valve mounting bolts. Do not remove.
6. Remove EGR crossover tube clamp (5).
7. Remove EGR crossover tube clamp (3).
8. Remove EGR crossover tube clamp (1 and 3). 1 - NUTS 2 - EGR COOLER 3 - LOCKING CONSTANT TENSION CLAMPS 4 - EGR CROSSOVER TUBE CLAMP 5 - EGR CROSSOVER TUBE 6 - FRONT COOLANT TUBE 7 - BREATHER TUBE 8 - REAR COOLANT TUBE
9. Using Tool 6094, remove forward coolant tube (6) from EGR cooler (2).
10. Using Tool 6094, remove breather tube (7).
11. Using Tool 6094, remove rear coolant tube (8) from EGR cooler (2).
12. Remove EGR Transfer Connection Tube from casting, (if equipped).
13. Remove EGR cooler flange nuts (1).
14. Remove EGR cooler mount bolts.
15. Remove EGR cooler. Discard flange gasket.
16. If damaged, remove EGR Cooler support bracket.

OPERATION-5.9L DIESEL

The transmission oil is routed through the oil-to water cooler first, then to the air-to-oil cooler where additional heat is removed from the transmission oil before returning to the transmission. The auxiliary air-to-oil cooler has an internal thermostat that controls fluid flow through the cooler. When the transmission fluid is cold (less then operating temperature), the fluid is routed through the cooler bypass. When the transmission fluid reaches operating temperatures and above, the thermostat closes off the bypass allowing fluid flow through the cooler. The thermostat is serviceable.

OPERATION-GAS

Transmission oil is routed through the cooler where heat is removed from the transmission oil before returning to the transmission.

Scheme 27

1. Place a drain pan under the oil cooler lines.
2. Disconnect the transmission oil cooler line quick-connect fitting at the cooler outlet. See «STANDARD PROCEDURE»(ref-303804-S37961335992008103100000) . Plug the cooler lines to prevent oil leakage.
3. Unsnap the transmission cooler tubes from the radiator tank clips.
4. Remove the bolt attaching the transmission cooler to the radiator.
5. Remove oil cooler from the vehicle. Take care not to damage the radiator core or transmission cooler tubes.