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 gasket sealing.

Warnings

Tools required

Parts

• Water pump assembly with gasket × 1 — Mopar 5086588AA or equivalent
• Serpentine belt × 1 — Replace if worn or cracked
• Thermostat and gasket × 1 — Recommended to replace while accessible
• Coolant hose clamps × 4 — Constant tension spring clamps preferred
• RTV silicone sealant × 1 — High-temp red RTV gasket maker

Fluids

• Ethylene glycol 50/50 (green conventional early, HOAT later) — 28 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow engine to cool completely (minimum 2 hours)
3. Disconnect negative battery cable
4. Place drain pan under radiator and open petcock to drain coolant completely
5. Remove radiator cap only after system is fully depressurized and cool
6. Clean engine bay around water pump area to prevent debris from entering cooling system

Procedure

1. 1

   Remove serpentine belt and fan assembly
   Use a 15mm wrench or serpentine belt tool to rotate the tensioner clockwise and slip the belt off the pulleys. Remove the belt completely. If equipped with a viscous fan clutch, remove the four fan shroud bolts and slide shroud back toward radiator. The fan/fan clutch assembly bolts to the water pump hub on the Cummins. Remove the fan mounting bolts (right-hand thread) while holding the hub from rotating. Verify fastener type before removal.
2. 2

   Remove fan and pulley assembly
   Hold the water pump hub from rotating with a holding tool and remove the fan/fan clutch mounting bolts to separate the fan assembly. Remove the water pump pulley bolts and remove the pulley. Set aside all components in order for reinstallation.
3. 3

   Disconnect coolant hoses from water pump
   Identify the upper radiator hose and heater hoses connected to the water pump housing. Use pliers to release hose clamps and slide them back away from connections. Carefully twist and pull hoses off the pump fittings. If hoses are stuck, use a small flat screwdriver to break the seal, being careful not to damage the hose ends. Expect residual coolant to drain from hoses.
4. 4

   Remove thermostat housing if necessary
   On some model years, the thermostat housing may obstruct water pump removal. If needed, remove the thermostat housing bolts and carefully separate the housing from the engine block. Keep the thermostat and gasket for inspection - replacement is recommended while accessible.
   Torque spec

   Thermostat Housing Bolt15 Nm (11 lb-ft)
5. 5

   Remove water pump mounting bolts
   The Cummins water pump is secured by multiple bolts (typically 7-8 bolts of varying lengths). Note the location and length of each bolt as they are not all the same. Remove all bolts in a criss-cross pattern, working from outside to center. Support the water pump while removing the last bolts to prevent it from dropping.
6. 6

   Remove old water pump
   Carefully pull the water pump assembly away from the engine block. It may require light tapping with a rubber mallet or careful prying with a pry bar at designated pry points (never pry on machined gasket surfaces). Once free, remove the pump and inspect the pump cavity for debris or corrosion. Check the impeller shaft area for any signs of leakage into the engine.
7. 7

   Clean mounting surface and inspect
   Using a plastic or brass gasket scraper, completely remove all old gasket material from the engine block mounting surface. Do not use steel scrapers that could damage the aluminum surface. Clean thoroughly with degreaser and wipe dry. Inspect the mounting surface for gouges, pitting, or warping. Use a wire brush to clean bolt holes and remove any rust or debris. Blow out bolt holes with compressed air if available.
8. 8

   Prepare and install new water pump
   Inspect the new water pump for shipping damage and verify gasket is included. Some pumps require a thin bead of RTV sealant on the gasket, while others use a dry gasket - follow manufacturer instructions. Position the gasket on the pump or engine block (whichever is specified). Carefully align the new water pump to the mounting surface, ensuring the gasket stays in position. Start all mounting bolts by hand before tightening any.
9. 9

   Torque water pump bolts to specification
   Using a torque wrench, tighten the water pump mounting bolts in a criss-cross pattern starting from the center and working outward. This ensures even pressure on the gasket and prevents warping. Torque all bolts to specification in at least two passes: first to 50% of final torque, then to final specification. Verify all bolts are properly seated.
   Torque spec

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

    Reinstall thermostat housing if removed
    If the thermostat housing was removed, install a new thermostat with a new gasket or O-ring as applicable. Clean the mounting surface on both the housing and block. Position the thermostat with the spring side down (toward engine). Install the housing and tighten bolts evenly to specification.
    Torque spec

    Thermostat Housing Bolt15 Nm (11 lb-ft)
11. 11

    Reconnect coolant hoses
    Inspect all coolant hoses for cracks, softness, or deterioration - replace any questionable hoses. Slide new constant tension spring clamps onto hoses before installation. Push hoses firmly onto water pump and thermostat housing fittings until fully seated. Position clamps 1/4 inch from hose ends and ensure they are properly engaged on the fittings.
    Torque spec

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

    Reinstall pulley and fan assembly
    Mount the water pump pulley to the pump hub and install bolts finger-tight. Install the fan/fan clutch assembly onto the water pump hub with its mounting bolts, holding the hub from rotating. Torque the fan bolts to specification. Then fully tighten the pulley bolts. Reinstall the fan shroud if removed, ensuring proper clearance around the fan blades.
13. 13

    Install serpentine belt
    Route the new or inspected serpentine belt around all pulleys according to the belt routing diagram (typically found on the fan shroud or radiator support). Use the belt tensioner tool to rotate the tensioner and slip the belt onto the last pulley. Verify the belt is properly seated in all pulley grooves and release the tensioner slowly. Double-check belt alignment on all pulleys.
14. 14

    Refill cooling system
    Close the radiator petcock drain. Mix fresh coolant to 50/50 ratio if using concentrate, or use pre-mixed coolant appropriate for your model year (green conventional for pre-1998.5, HOAT for 1998.5+). Using a coolant funnel with adapter at the radiator cap, slowly fill the system to allow air to escape. Fill until coolant reaches the full mark. Squeeze upper radiator hose several times to help purge air. Top off as needed. Replace radiator cap.
15. 15

    Bleed air and test for leaks
    Reconnect negative battery cable. Start the engine and allow it to warm up to operating temperature while monitoring coolant level and temperature gauge. Run heater on high to circulate coolant through heater core. Watch for leaks around water pump, hoses, and thermostat housing. As the thermostat opens, coolant level may drop - shut engine off when at operating temperature, allow to cool slightly, and top off coolant as needed. After coolant level stabilizes, install radiator cap fully.

Reassembly

1. Verify all hose clamps are properly tightened and positioned
2. Ensure fan has adequate clearance from shroud and radiator
3. Check serpentine belt tension and alignment on all pulleys
4. Confirm all tools and parts have been removed from engine bay

Verification

• Start engine and verify no coolant leaks from water pump, hoses, or thermostat housing
• Confirm coolant temperature stays within normal operating range (190-210°F)
• Check that heater produces hot air when set to maximum temperature
• Verify coolant level is stable after several heat cycles
• Listen for any unusual bearing noise from water pump or fan clutch
• Inspect under vehicle for coolant drips after test drive
• Monitor coolant level for first 100 miles and top off as needed after air purges

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