Replace the serpentine belt idler pulley on the 6.7L Cummins diesel engine to eliminate noise or bearing failure.

Warnings

Tools required

Parts

• Serpentine belt idler pulley × 1 — Mopar 68066850AA or equivalent
• Serpentine belt (if worn or damaged) × 1 — Use OEM specification

Preparation

1. Park vehicle on level ground and engage parking brake
2. Allow engine to cool completely
3. Disconnect negative battery cable
4. Photograph or sketch serpentine belt routing before removal
5. Inspect belt routing diagram on fan shroud if present

Procedure

1. 1

   Access the serpentine belt
   Open hood and locate the serpentine belt system on the front of the 6.7L Cummins engine. Identify the belt tensioner, idler pulley, and all driven accessories. The idler pulley is typically positioned between the alternator and power steering pump.
2. 2

   Release belt tension
   Using a 3/8" breaker bar or serpentine belt tool, insert into the square hole on the automatic belt tensioner. Rotate the tensioner clockwise to release tension on the belt. The tensioner spring is strong, so use steady controlled force.
3. 3

   Remove serpentine belt
   While holding tension released, slip the serpentine belt off one of the pulleys (alternator pulley recommended). Slowly release tensioner back to rest position. Remove belt completely from engine compartment and set aside for inspection.
4. 4

   Inspect idler pulley condition
   Spin the idler pulley by hand to check for roughness, grinding, or noise. Check for lateral play or wobble. Confirm this is the pulley requiring replacement. Inspect other pulleys and tensioner for wear while belt is removed.
5. 5

   Remove idler pulley mounting bolt
   Using a 15mm socket, remove the idler pulley center mounting bolt. Turn counterclockwise to loosen. The bolt threads into the engine bracket or front cover. Keep bolt for comparison if reusing.
   Torque spec

   Idler Pulley Bolt45 Nm (33 lb-ft)
6. 6

   Remove idler pulley
   Pull the idler pulley straight off the mounting stud or bracket. Note the position of any spacers or washers behind the pulley. Clean the mounting surface of any dirt or debris with a clean rag.
7. 7

   Install new idler pulley
   Position the new idler pulley onto the mounting bracket, ensuring any spacers or washers are in their original positions. Verify the pulley rotates freely before installing the bolt. Start the mounting bolt by hand to ensure proper thread engagement.
8. 8

   Torque idler pulley bolt
   Using a torque wrench, tighten the idler pulley mounting bolt to 45 Nm (33 lb-ft). Hold the pulley steady if necessary to prevent spinning during final torque. Verify pulley still rotates smoothly after torquing.
   Torque spec

   Idler Pulley Bolt45 Nm (33 lb-ft)
9. 9

   Reinstall serpentine belt
   Route the serpentine belt around all pulleys according to your photo or the diagram on the fan shroud. Leave the belt off one pulley (typically alternator) for final installation. Double-check routing matches diagram exactly before tensioning.
10. 10

    Tension and seat belt
    Use the breaker bar to rotate the belt tensioner clockwise again. Slip the belt onto the final pulley while holding tension released. Slowly release the tensioner to apply proper tension to the belt. Verify belt is properly seated in all pulley grooves.
11. 11

    Verify belt alignment
    Visually inspect that the serpentine belt is centered on all pulleys and properly seated in all grooves. The belt should not be riding on pulley edges or twisted. Manually rotate the engine crank pulley two full revolutions to ensure proper tracking.

Reassembly

1. Reconnect negative battery cable
2. Close hood and secure properly

Verification

• Start engine and listen for unusual squealing, chirping, or grinding noises from belt area
• Observe belt operation for 30 seconds to ensure proper tracking and no slipping
• Check that all accessories (alternator, power steering, A/C compressor) are operating normally
• Rev engine to 2000 RPM briefly and verify no belt slip or noise occurs
• Shut off engine and perform final visual inspection of belt alignment on all pulleys

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