Harmonic Balancer

This procedure covers removal and replacement of the harmonic balancer (crankshaft damper) on the 5.9L Cummins diesel engine, requiring removal of the radiator and fan assembly for access.

Warnings

Tools required

Parts

• Harmonic balancer/crankshaft damper × 1 — Use OEM Cummins or quality aftermarket (Fluidampr/Dorman)
• Crankshaft bolt × 1 — OEM recommended - one-time use
• Lower radiator hose × 1 — Replace if damaged during removal
• Accessory drive belt × 1 — Inspect and replace if worn

Fluids

• HOAT coolant 50/50 — 4 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Disconnect both battery cables, negative first
3. Allow engine to cool completely (minimum 2 hours)
4. Remove engine cover and air intake system
5. Place large drain pan under radiator and open petcock to drain coolant
6. Remove upper and lower radiator hoses
7. Disconnect transmission cooler lines from radiator (plug lines to prevent leakage)
8. Label and disconnect any electrical connections to radiator fan or sensors

Procedure

1. 1

   Remove fan shroud and radiator
   Remove the fan shroud mounting bolts and lift shroud up and over the fan assembly. Remove radiator mounting bolts and carefully lift radiator out of engine bay. Inspect radiator support and AC condenser for damage. Set radiator aside safely.
2. 2

   Remove fan clutch assembly
   Using the appropriate fan clutch wrench, hold the water pump pulley and remove the fan clutch assembly from the water pump. Verify the correct wrench size against Cummins service documentation. Note that the fan clutch uses a RIGHT-HAND thread - turn counterclockwise to loosen. Remove fan and clutch assembly as a unit and set aside safely.
3. 3

   Remove accessory drive belt
   Rotate the serpentine belt tensioner to release tension and remove the accessory drive belt. Inspect belt for cracks, glazing, or excessive wear. Mark routing if necessary for reinstallation, though diagram should be on fan shroud.
4. 4

   Access crankshaft bolt
   The crankshaft bolt is now accessible at the center of the harmonic balancer. Clean area around bolt and balancer hub to prevent debris from entering engine. Inspect balancer for visible damage, rubber separation, or wobble.
5. 5

   Lock crankshaft rotation
   Install crankshaft holding tool or flywheel locking tool through bellhousing access hole to prevent crankshaft rotation. Alternatively, place transmission in gear and set parking brake firmly (manual transmission preferred). The bolt is extremely tight and requires significant force to break loose.
6. 6

   Remove crankshaft bolt
   Using a large breaker bar or impact wrench, remove the crankshaft center bolt. This bolt is very tight and may require significant effort to break loose. Turn counterclockwise to loosen. Remove bolt and washer completely and set aside (do not reuse old bolt).
7. 7

   Install harmonic balancer puller
   Thread a 3-jaw harmonic balancer puller onto the balancer, ensuring the jaws grip behind the outer ring and the center screw contacts the crankshaft snout (use a protective cap if provided). Do NOT pry against the timing cover or use a gear puller that contacts the outer ring only.
8. 8

   Remove harmonic balancer
   Slowly tighten the puller center bolt to draw the balancer off the crankshaft. Apply steady pressure - the balancer should release with moderate force. If excessive force is required, stop and verify puller is properly positioned. Remove balancer and puller assembly.
9. 9

   Inspect crankshaft and seal
   Thoroughly inspect the crankshaft snout for scoring, burrs, or damage. Check the front crankshaft seal for leakage. Clean the crankshaft snout with a wire brush and solvent, removing any rust or debris. Inspect the timing cover area for oil leaks. If seal is leaking, this is an ideal time to replace it.
10. 10

    Prepare new harmonic balancer
    Inspect new harmonic balancer for shipping damage. Verify the keyway in the balancer aligns with the key on the crankshaft. Lightly oil the crankshaft snout and inside bore of the balancer hub with clean engine oil. Do NOT use anti-seize or excessive lubricant.
11. 11

    Install harmonic balancer
    Align the keyway in the balancer with the key on the crankshaft. Slide balancer onto crankshaft as far as it will go by hand. Install the harmonic balancer installation tool (threaded installer) and slowly draw the balancer into position. The balancer must be fully seated against the crankshaft shoulder - verify with measurements or marks. Never hammer the balancer onto the crankshaft.
12. 12

    Install crankshaft bolt
    Install NEW crankshaft bolt with washer. Apply a small amount of medium-strength thread locker to bolt threads if specified by manufacturer. With crankshaft still locked, hand-thread bolt to prevent cross-threading. Note: Consult factory service manual or Cummins technical documentation for the proper torque sequence. The Cummins damper bolt typically uses an initial torque followed by a specified additional rotation angle; verify exact values before final torque.
13. 13

    Reinstall accessory drive belt
    Route serpentine belt around all pulleys according to routing diagram. Use tensioner tool to rotate tensioner and slip belt into place. Verify belt is properly seated in all pulley grooves and release tensioner.
14. 14

    Reinstall fan clutch
    Thread fan clutch assembly back onto water pump shaft. Remember RIGHT-HAND threads - turn clockwise to tighten. Torque to specification per service manual (typically hand tight plus additional rotation with fan clutch wrench).
15. 15

    Reinstall radiator and fan shroud
    Carefully lower radiator back into position, ensuring it seats properly on mounting brackets. Install radiator mounting bolts. Position fan shroud over fan assembly and install shroud mounting bolts. Reconnect transmission cooler lines and all electrical connections. Reinstall radiator hoses with new clamps if needed.

Reassembly

1. Refill cooling system with HOAT 50/50 coolant mixture, approximately 4 quarts or until full
2. Reinstall air intake system and engine cover
3. Reconnect battery cables, positive first then negative
4. Start engine and check for coolant leaks at radiator connections
5. Allow engine to reach operating temperature and verify cooling fan operation
6. Check coolant level after engine cools and top off as needed
7. Inspect accessory belt alignment and verify all pulleys rotate smoothly

Verification

• Start engine and listen for unusual noises from front of engine - harmonic balancer should run smoothly without wobble or vibration
• Verify accessory belt tracks properly on all pulleys without misalignment
• Check for coolant leaks at all radiator connections
• With engine at idle, visually inspect harmonic balancer for any wobble or runout (should spin true)
• Test drive vehicle and verify no new vibrations at various RPM ranges
• Recheck crankshaft bolt torque after initial warm-up cycle if recommended by manufacturer
• Monitor for oil leaks from front crankshaft seal area over next few days

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