Fan Belt Replacement

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

Warnings

Tools required

Parts

• Serpentine belt (8-rib) × 1 — Gates K080915 or equivalent

Preparation

1. Park vehicle on level ground and engage parking brake
2. Allow engine to cool completely for at least 30 minutes
3. Open hood and secure with prop rod
4. Locate the belt routing diagram on the fan shroud or radiator support. If diagram is missing or faded, take clear photos of the current belt routing from multiple angles

Procedure

1. 1

   Inspect current belt routing
   Before removing the belt, carefully trace and document the belt path around all pulleys including the crankshaft, water pump, power steering pump, idler pulley, tensioner pulley, air conditioning compressor (if equipped), and alternator. Note which side of the belt (ribbed or smooth) contacts each pulley.
2. 2

   Locate the belt tensioner
   Identify the automatic belt tensioner on the front of the engine. The tensioner pulley is spring-loaded and has a center bolt head (verify size against service documentation) that serves as the tension release point.
3. 3

   Release belt tension
   Using the correct socket size attached to a breaker bar, insert the tool into the tensioner bolt head. Rotate the tensioner in the direction indicated by the tensioner arm/service documentation to release tension on the belt. This requires significant force. Hold the tensioner in the released position.
4. 4

   Remove the old belt
   While holding tension released with the breaker bar, slip the serpentine belt off the tensioner pulley first, then off the alternator pulley. Slowly release the tensioner back to its resting position. Remove the belt from the remaining pulleys and extract it 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 excessive play. Inspect the tensioner arm movement for smooth operation and proper spring return. Check all pulley surfaces for cracks, damage, or excessive wear grooves. Replace any damaged components before installing the new belt.
6. 6

   Route the new belt
   Starting at the crankshaft pulley at the bottom of the engine, route the new belt around all pulleys EXCEPT the tensioner pulley, following your documented routing diagram. Ensure the ribbed side of the belt contacts all grooved pulleys properly. The belt should fit snugly in all pulley grooves without forcing.
7. 7

   Install belt onto tensioner
   Using the correct socket and breaker bar, rotate the tensioner in the release direction again to relieve tension. While holding the tensioner in the released position, guide the belt over the tensioner pulley ensuring the ribs seat properly in the pulley grooves. Slowly and carefully release the tensioner to apply proper tension to the belt.
8. 8

   Verify belt alignment and seating
   Visually inspect the entire belt path to ensure the belt is properly seated in all pulley grooves and aligned correctly. The belt should not be twisted and should ride centered on all pulleys. Check that the belt ribs are fully seated in all grooved pulleys.
9. 9

   Check tensioner position
   Verify the automatic tensioner is within its normal operating range. The tensioner arm should be positioned approximately mid-range of its travel, not fully extended or fully compressed. If the tensioner is at either extreme, the wrong belt length has been installed.

Reassembly

1. Ensure all tools are removed from the engine compartment
2. Close and secure hood

Verification

• Start the engine and allow it to idle. Listen for any squealing, chirping, or unusual noises from the belt area
• Observe the belt operation for the first 30 seconds to ensure it runs smoothly without slipping or jumping on pulleys
• Turn on electrical loads (headlights, air conditioning, radio) to verify the belt handles increased alternator and A/C compressor load without slipping
• Shut off engine and perform a final visual inspection to confirm the belt remains properly seated on all pulleys
• After 100-200 miles of driving, recheck belt condition and seating as the new belt will seat itself during the break-in period

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