Dodge Durango (HB). Manual - part 137

WATER PUMP BYPASS - 4.7L

The 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 pre-
venting the coolant from flowing through the radiator.
The thermostat (4) uses a stub shaft located at the
rear of the thermostat to control flow through the
bypass gallery.

OPERATION

WATER PUMP

A centrifugal water pump circulates coolant through the water jackets, passages, intake manifold, radiator core, cool-
ing 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.

WATER PUMP BYPASS - 4.7L ENGINE

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 nor-
mal temperature operation.

REMOVAL

3.7L/4.7L ENGINE

The water pump on 3.7L/4.7L engines is bolted directly
to the engine timing chain case cover.

1. Disconnect negative battery cable.

2. Drain cooling system (Refer to 7 - COOLING -

STANDARD PROCEDURE).

ENGINE

7 - 43

3. Remove fan/viscous fan drive assembly from water

pump (Refer to 7 - COOLING/ENGINE/RADIATOR
FAN - REMOVAL). Do not attempt to remove fan/
viscous fan drive assembly from vehicle at this
time.

4. If water pump is being replaced, do not unbolt fan

blade assembly from thermal viscous fan drive.

5. Remove two fan shroud-to-radiator screws. Discon-

nect the coolant overflow hose, windshield washer
fluid hose and washer pump electrical connector.

6. Remove fan shroud and fan blade/viscous fan drive

assembly from vehicle.

7. After removing fan blade/viscous fan drive assem-

bly, do not place thermal viscous fan drive in hor-
izontal position. If stored horizontally, silicone fluid
in viscous fan drive could drain into its bearing
assembly and contaminate lubricant.

8. Remove accessory drive belt from the water pump

pulley (2) (Refer to 7 - COOLING/ACCESSORY
DRIVE/DRIVE BELTS - REMOVAL).

9. Remove lower radiator hose clamp and remove

lower hose at water pump.

10. Remove seven water pump mounting bolts and

one stud bolt.

CAUTION: Do not pry water pump at timing chain
case/cover. The machined surfaces may be dam-
aged resulting in leaks.

11. Remove water pump and gasket. Discard gasket.

5.7L ENGINE

1. Disconnect negative battery cable.

2. Drain cooling system (Refer to 7 - COOLING -

STANDARD PROCEDURE)

3. Remove fan/viscous fan drive assembly from water

pump (Refer to 7 - COOLING/ENGINE/RADIATOR
FAN - REMOVAL). Do not attempt to remove fan/
viscous fan drive assembly from vehicle at this
time.

7 - 44

ENGINE

4. If water pump is being replaced, do not unbolt fan

blade assembly from thermal viscous fan drive.

5. Remove two fan shroud-to-radiator screws. Discon-

nect the coolant overflow hose, windshield washer
fluid hose and washer pump electrical connector.

6. Remove fan shroud and fan blade/viscous fan drive

assembly from vehicle.

7. Remove A/C compressor and generator brace.

8. Remove idler pulleys.

9. Remove belt tensioner assembly (Refer to 7 -

COOLING/ACCESSORY DRIVE/BELT TENSION-
ERS - REMOVAL).

10. Remove upper and lower radiator hoses.

11. Remove heater hoses.

12. Remove water pump mounting bolts and remove

pump.

CLEANING

Clean the gasket mating surface. Use caution not to damage the gasket sealing surface.

INSPECTION

Inspect the water pump assembly for cracks in the housing, water leaks from shaft seal, worn bearing or impeller
rubbing either the pump body or timing chain case/cover.

INSTALLATION

3.7/4.7L ENGINE

1. Clean gasket mating surfaces.

2. Using a new gasket, position water pump (1) and

install mounting bolts as shown. Tighten water
pump mounting bolts to 58 N·m (43 ft. lbs.) torque.

3. Spin water pump to be sure that pump impeller

does not rub against timing chain case/cover.

4. Connect radiator lower hose to water pump.

ENGINE

7 - 45

5. Install accessory drive belt (Refer to 7 - COOLING/

ACCESSORY DRIVE/DRIVE BELTS - INSTALLA-
TION).

6. Position fan shroud and fan blade/viscous fan drive

assembly.

7. Install two fan shroud-to-radiator screws.

8. Be sure of at least 25 mm (1.0 inches) between

tips of fan blades and fan shroud.

9. Install fan blade/viscous fan drive assembly to

water pump shaft (Refer to 7 - COOLING/ENGINE/
RADIATOR FAN - INSTALLATION).

10. Fill cooling system (Refer to 7 - COOLING -

STANDARD PROCEDURE).

11. Connect negative battery cable.

12. Start and warm the engine. Check for leaks.

5.7L ENGINE

1. Install water pump and mounting bolts. Tighten

moubting bolts to 24 N·m (18 ft. lbs.).

2. Install heater hoses.

3. Install upper and lower radiator hoses.

4. Install belt tensioner assembly (Refer to 7 - COOL-

ING/ACCESSORY DRIVE/BELT TENSIONERS -
INSTALLATION).

5. Install idler pulleys.

6. Install

A/C

compressor

and

alternator

brace.

Tighten bolt and nuts to 28 N·m (21 ft. lbs.).

7. Install fan shroud assembly and two fan shroud

mounting screws.

8. Install the fan/viscous fdrive assembly (Refer to 7 -

COOLING/ENGINE/RADIATOR FAN - INSTALLA-
TION).

9. Be sure of at least 25 mm (1.0 inches) between

tips of fan blades and fan shroud.

10.

Install accessory drive belt (Refer to 7 - COOL-

ING/ACCESSORY

DRIVE/DRIVE

BELTS

INSTALLATION).

11. Connect negative battery cable.

12. Fill coolant (Refer to 7 - COOLING - STANDARD

PROCEDURE).

13. Pressure test coolant system (Refer to 7 - COOL-

ING - DIAGNOSIS AND TESTING).

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ENGINE

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