Front Main Seal

This procedure replaces the front crankshaft seal on the 5.9L Cummins diesel engine, requiring removal of the radiator, fan assembly, and harmonic balancer to access the seal.

Warnings

Tools required

Parts

• Front crankshaft seal × 1 — Use OEM Mopar specification
• Harmonic balancer bolt × 1 — Replace if loosened, use OEM
• Coolant (HOAT 50/50) × 2 — Mopar HOAT or equivalent
• RTV silicone sealant × 1 — High-temp oil-resistant

Fluids

• HOAT coolant 50/50 — 2 qt

Preparation

1. Park vehicle on level ground and engage parking brake
2. Disconnect both battery cables, negative first
3. Allow engine to cool completely if recently operated
4. Raise front of vehicle and support securely on jack stands
5. Remove engine skid plate if equipped
6. Place drain pan under radiator and note coolant level for refill reference

Procedure

1. 1

   Drain cooling system
   Open radiator petcock at bottom of radiator and drain coolant into appropriate container. If petcock is not functional, remove lower radiator hose at radiator. Drain approximately 2 gallons to drop level below radiator outlet.
2. 2

   Remove upper radiator components
   Remove upper radiator hose from radiator. Disconnect overflow hose from radiator. Remove radiator shroud mounting bolts (typically four bolts) and lift shroud up and back, resting it on fan assembly. On some configurations, the shroud may need to be completely removed.
3. 3

   Remove fan assembly
   Using appropriate fan clutch wrenches, remove the fan clutch assembly from the fan drive/water pump. On the 5.9L Cummins the fan clutch nut is a standard right-hand thread (loosen counterclockwise). Hold the pulley stationary while loosening the fan clutch nut. Remove fan and clutch assembly as a unit. Remove fan shroud completely.
4. 4

   Remove drive belts and accessories
   Note routing of serpentine belt or mark with paint if necessary. Release belt tensioner and remove drive belt(s). Remove water pump pulley bolts and remove pulley. If equipped with A/C, remove A/C compressor mounting bolts and secure compressor aside without disconnecting refrigerant lines.
5. 5

   Remove radiator
   Disconnect lower radiator hose from radiator. Disconnect transmission cooler lines if equipped with automatic transmission (catch ATF spillage). Remove radiator mounting bolts or brackets and carefully lift radiator out of vehicle. This provides necessary clearance for harmonic balancer removal.
6. 6

   Remove harmonic balancer bolt
   Remove crankshaft pulley bolts and remove pulley from harmonic balancer. Place transmission in gear or use a holding tool to prevent crankshaft rotation. Using an appropriate socket, remove the harmonic balancer/vibration damper retaining bolts (the Cummins damper is secured by multiple perimeter bolts, not a single center bolt). Prevent crankshaft rotation using a holding tool. Inspect bolts and replace per Cummins service specification.
7. 7

   Remove harmonic balancer
   After removing the perimeter retaining bolts, slide the vibration damper off the crankshaft flange. The Cummins damper is bolt-retained (not press-fit on a taper); a puller is generally not required. Support the damper and avoid prying against the front cover or damaging the crankshaft. Never hammer on the crankshaft or damper.
8. 8

   Remove front seal
   Inspect the front timing cover area around the seal for damage. Using a seal puller or carefully positioned pry bar, extract the old front seal from the timing cover. Work around the seal circumference to avoid damaging the timing cover bore. Remove any old seal material or debris from the bore.
9. 9

   Prepare and install new seal
   Clean the seal bore thoroughly with solvent and allow to dry. Inspect crankshaft seal surface on harmonic balancer hub for grooves or damage. Lightly coat the outer diameter of new seal with RTV sealant. Coat seal lip with clean engine oil. Position seal squarely in bore with lip facing inward toward engine.
10. 10

    Drive seal into position
    Using a seal driver tool or appropriately sized socket that contacts only the outer seal edge (not the center), carefully drive the seal into the timing cover bore. Drive seal in evenly until flush with timing cover face or to specified depth per manufacturer instructions. Verify seal is seated evenly around entire circumference.
11. 11

    Reinstall harmonic balancer
    Verify crankshaft flange and damper mating surfaces are clean and dry. Align the damper to the crankshaft flange (via the alignment dowel/pilot as applicable). Reinstall the damper against the crankshaft flange. The Cummins damper is bolt-retained and does not require a press installer tool.
12. 12

    Install new balancer bolt and torque
    Install the vibration damper retaining bolts. Hold the crankshaft from rotating using previous method. Torque the damper bolts to Cummins specification (commonly approximately 92 ft-lbs each in a crossing pattern — verify exact spec and pattern for your engine; no torque-angle step applies). Reinstall crankshaft pulley as applicable.
13. 13

    Reinstall cooling system and accessories
    Reinstall radiator and secure with mounting bolts. Reconnect transmission cooler lines if equipped. Install lower radiator hose. If A/C compressor was removed, reinstall and secure. Install water pump pulley. Route and install drive belt(s) per original routing. Install fan clutch assembly onto water pump shaft (remember reverse threads if applicable).
14. 14

    Complete reassembly
    Install radiator shroud and secure with mounting bolts. Reconnect upper radiator hose and overflow hose. Close radiator petcock. Refill cooling system with HOAT 50/50 coolant mixture. Reconnect battery cables, positive first. Lower vehicle from jack stands.
15. 15

    Start and check for leaks
    Start engine and allow to reach operating temperature with heater on full hot to purge air from cooling system. Monitor coolant level and add as necessary. Inspect front seal area closely for any oil leakage. Check coolant system for leaks at all connection points. Allow engine to run for 10-15 minutes, then shut off and recheck coolant level when cool.

Reassembly

1. Torque all fasteners to specification when available
2. Replace harmonic balancer bolt with new OEM part
3. Verify drive belt routing matches factory configuration before starting engine
4. Bleed cooling system completely to avoid overheating

Verification

• Run engine at idle for 15 minutes and inspect front seal area for oil leaks
• Check for coolant leaks at all radiator connections
• Verify no unusual vibrations from harmonic balancer installation
• Recheck coolant level after engine reaches operating temperature and cools
• Test drive vehicle and recheck front seal area for leaks after 50-100 miles

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