Serpentine Belt

This procedure covers removal and installation of the serpentine belt on the 5.9L Cummins diesel engine, including belt routing verification and tensioner operation.

Warnings

Tools required

Parts

• Serpentine belt × 1 — Use OEM specification or Gates K060988

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow engine to cool completely if recently operated
3. Locate and photograph belt routing diagram on radiator shroud or fan shroud
4. Inspect belt tensioner and idler pulley for noise, roughness, or excessive play before beginning

Procedure

1. 1

   Access the serpentine belt
   Open the hood and secure with prop rod. Locate the serpentine belt on the front of the engine. The belt routes around the crankshaft pulley, water pump, power steering pump, alternator, A/C compressor (if equipped), fan hub/idler pulley, and the automatic tensioner located on the front of the engine. Verify the exact routing against the underhood diagram before proceeding.
2. 2

   Document belt routing
   Verify the belt routing matches the diagram on the fan shroud or radiator support. If no diagram is present, sketch or photograph the current belt path around all pulleys, noting which side of the belt contacts each pulley (smooth vs ribbed side).
3. 3

   Relieve belt tension
   Locate the spring-loaded automatic belt tensioner on the front of the engine. Fit a 15mm socket or box-end wrench onto the tensioner pulley bolt (or use the square drive with a 3/8" breaker bar). Rotate the tensioner in the direction that unloads the belt (verify against the tensioner's swing-arc; typically counterclockwise) to relieve tension. The tensioner arm will swing through its release travel.
4. 4

   Remove the old belt
   While holding the tensioner in the released position, slip the serpentine belt off the nearest pulley (typically the alternator or water pump pulley). Slowly release tension on the tensioner arm, allowing it to return to its rest position. Route the old belt out from around the crankshaft pulley and other components, then remove it completely from the engine bay.
5. 5

   Inspect pulleys and tensioner
   With the belt removed, manually spin each pulley to check for bearing noise, roughness, or wobble. Check the tensioner arm for smooth movement and verify the tensioner spring provides adequate resistance. Inspect all pulley surfaces for wear grooves, damage, or contamination from oil or coolant. Replace any worn components before installing the new belt.
6. 6

   Route the new belt
   Starting at the crankshaft pulley, route the new serpentine belt around all pulleys except the one you plan to slip it onto last (typically the alternator or water pump). Ensure the ribbed side of the belt contacts the grooved pulleys correctly. The backside (smooth side) should only contact the tensioner pulley and any smooth idler pulleys. Verify routing matches your diagram or photo.
7. 7

   Install belt onto final pulley
   Using the 15mm wrench or 3/8" breaker bar, rotate the tensioner in the belt-release direction again to relieve tension. Position the belt over the final pulley while holding the tensioner in the released position. Verify the belt is properly seated in all pulley grooves before releasing the tensioner.
8. 8

   Release tensioner and verify installation
   Slowly release the tensioner arm, allowing it to apply proper tension to the new belt. Visually verify the belt is centered and fully seated in all pulley grooves. Check that the belt ribs align properly with the pulley grooves on all components. The tensioner arm should be positioned approximately in the middle of its travel range when properly tensioned.
9. 9

   Check belt tension and alignment
   Manually rotate the crankshaft pulley two complete revolutions by hand (using a wrench on the crankshaft bolt if necessary) to ensure the belt tracks properly and does not slip off any pulleys. Verify the belt maintains proper alignment throughout the entire rotation. Check that the tensioner moves smoothly as the belt rotates.
10. 10

    Start engine and verify operation
    Start the engine and observe belt operation for the first 30 seconds. Listen for any squealing, chirping, or unusual noises that might indicate misalignment or improper tension. Turn the steering wheel lock-to-lock and activate the air conditioning to verify belt performs properly under all accessory loads. If any noise or slipping occurs, shut off the engine and recheck belt routing and seating.

Reassembly

1. No disassembly was required for this procedure

Verification

• Start the engine and verify no belt squeal or chirping noises are present
• Confirm all accessories operate properly (alternator charging, power steering assist, A/C compressor engagement)
• Visually verify belt tracks centered on all pulleys with engine running
• Check that belt tensioner arm is positioned in the normal operating range (approximately centered)
• Recheck belt alignment after first 100 miles of operation and verify no edge wear or misalignment has occurred

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