Water Pump

This procedure covers removal and replacement of the water pump on the 5.9L Cummins diesel engine, including coolant drainage, accessory removal, and proper torque specifications.

Warnings

Tools required

Parts

• Water pump assembly with gasket × 1 — Use OEM Cummins specification
• Water pump gasket (if not included with pump) × 1 — Use OEM specification
• Coolant hose clamps (spring type preferred) × 4 — Various sizes as needed
• Serpentine belt (if worn or cracked) × 1 — Inspect and replace if needed

Fluids

• HOAT coolant 50/50 — 28 qt

Preparation

1. Ensure engine is completely cool to the touch
2. Disconnect negative battery cable
3. Raise and support front of vehicle on jack stands
4. Place large drain pan beneath engine to catch coolant
5. Remove engine skid plate if equipped

Procedure

1. 1

   Drain cooling system
   Open radiator petcock or remove lower radiator hose to drain coolant into collection pan. Remove radiator cap to allow complete drainage. Collect and properly dispose of used coolant according to local regulations.
2. 2

   Remove serpentine belt
   Locate the automatic belt tensioner on the front of the engine. Using a breaker bar or serpentine belt tool, rotate tensioner to release tension (verify rotation direction for your specific engine). Slide belt off pulleys. Slide belt off pulleys and remove. Note belt routing for reinstallation or take a photo before removal.
3. 3

   Remove fan shroud
   Remove upper fan shroud mounting bolts. The shroud may need to be loosened and moved back toward the radiator to provide clearance for water pump removal. Do not remove completely unless necessary for access.
4. 4

   Disconnect coolant hoses
   Using hose clamp pliers or standard pliers, release spring clamps or loosen worm-gear clamps on coolant hoses connected to water pump. Remove lower radiator hose and heater hose from pump. Have shop towels ready to catch residual coolant.
   Torque spec

   Hose Clamps3 Nm (2 lb-ft)
5. 5

   Remove water pump pulley
   Remove the bolts securing the water pump pulley/fan to the water pump hub (verify exact count against service manual). You may need to hold the pulley stationary while loosening bolts. Remove pulley and set aside.
6. 6

   Remove water pump mounting bolts
   Remove all water pump mounting bolts. On the 5.9L Cummins, the water pump is secured by a small number of cap screws (verify exact count against the service manual before removal). Note bolt locations as some may be different lengths. Carefully pull water pump away from engine block.
7. 7

   Clean mounting surfaces
   Thoroughly clean the water pump mounting surface on the engine front cover using a gasket scraper. Remove all old gasket material, corrosion, and debris. Use a wire brush if necessary. The surface must be completely clean and smooth for proper gasket seal. Inspect for any cracks or damage to the mounting surface.
8. 8

   Install new water pump
   Position new gasket on water pump or engine mounting surface according to gasket manufacturer instructions. Some gaskets may require a thin coat of gasket sealer. Align new water pump to mounting surface and start all bolts by hand. Ensure pump is seated flush against mounting surface before tightening.
   Torque spec

   Water Pump Bolts25 Nm (18 lb-ft)
9. 9

   Torque water pump bolts
   Using an even criss-cross pattern, tighten all water pump mounting bolts to the Cummins-specified torque (verify exact value in service manual; typically ~24 Nm / 18 lb-ft for M8 fasteners). Go around the pattern at least twice to ensure even torque distribution and proper gasket compression.
   Torque spec

   Water Pump Bolts25 Nm (18 lb-ft)
10. 10

    Reinstall water pump pulley
    Position water pump pulley on pump hub and install mounting bolts. Tighten bolts in a criss-cross pattern. These bolts should be snug but do not require torque specification - typical tightness is 30-40 lb-ft.
11. 11

    Reconnect coolant hoses
    Reconnect lower radiator hose and heater hose to water pump. Install new spring clamps or tighten worm-gear clamps snugly to fully seal the hose (no specific torque value is specified for hose clamps). Ensure hoses are fully seated on pump nipples before securing clamps.
    Torque spec

    Hose Clamps3 Nm (2 lb-ft)
12. 12

    Reinstall serpentine belt and fan shroud
    Reinstall serpentine belt following routing diagram. Rotate tensioner clockwise and slip belt over last pulley. Release tensioner slowly. Reinstall fan shroud and secure mounting bolts. Verify belt is properly seated in all pulley grooves.
13. 13

    Refill cooling system
    Close radiator petcock or reinstall lower radiator hose if it was removed for draining. Fill cooling system with 50/50 HOAT coolant mixture through the coolant fill/degas bottle (verify correct fill point for your cooling system configuration). Fill until coolant is visible at radiator neck. Install radiator cap. Fill coolant recovery tank to COLD fill line.
14. 14

    Bleed cooling system
    With radiator cap installed, start engine and allow to reach normal operating temperature with heater on high. Monitor temperature gauge closely. Once thermostat opens (temperature stabilizes), coolant level may drop. Shut off engine when cool, remove radiator cap, and top off coolant as needed. Repeat until level remains stable. Check for leaks around water pump gasket and all hose connections.

Reassembly

1. Reinstall engine skid plate if removed
2. Lower vehicle from jack stands
3. Reconnect negative battery cable
4. Double-check all hose connections and belt routing before final startup

Verification

• Start engine and verify no coolant leaks at water pump gasket or hose connections
• Confirm serpentine belt is tracking properly on all pulleys with no squealing
• Verify coolant temperature reaches normal operating range (180-200°F) and cooling fan cycles properly
• Check coolant level after engine reaches operating temperature and top off if necessary
• Test drive vehicle and recheck for leaks after cooling system reaches full pressure
• Verify heater produces hot air at idle and driving speeds

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