Idler Pulley

This procedure covers the replacement of the accessory drive belt idler pulley on the 3.5L EcoBoost V6 engine, including serpentine belt removal and reinstallation.

Warnings

Tools required

Parts

• Idler pulley assembly × 1 — Use OEM specification
• Serpentine belt (if worn or damaged) × 1 — Use OEM specification

Preparation

1. Ensure engine is completely cool to the touch
2. Park vehicle on level ground and engage parking brake
3. Disconnect negative battery cable to prevent accidental fan engagement
4. Take a photo of the serpentine belt routing for reference before removal

Procedure

1. 1

   Access engine compartment and locate components
   Open hood and secure with prop rod. Locate the serpentine belt, belt tensioner, and idler pulley on the front of the engine. The idler pulley is a smooth pulley (no grooves) typically positioned near the center of the accessory drive system. Verify belt routing matches the diagram on the radiator support or in the owner's manual.
2. 2

   Release belt tension and remove serpentine belt
   Using a 3/8" drive ratchet or breaker bar, insert tool into the square hole on the automatic belt tensioner. Rotate the tensioner clockwise to release tension on the belt. While holding tension released, slide the serpentine belt off one pulley (alternator recommended). Slowly release tensioner back to resting position. Remove belt completely from all pulleys and set aside.
3. 3

   Inspect idler pulley condition
   Spin the idler pulley by hand to check for roughness, grinding, or excessive play. Check for noise, bearing resistance, or wobble. If any of these conditions exist, replacement is necessary. Visually inspect the pulley surface for wear grooves or damage.
4. 4

   Remove idler pulley mounting bolt
   Using the appropriate metric socket, remove the idler pulley center mounting bolt by turning counterclockwise. The bolt may be a 13mm or 15mm head depending on specific pulley design. Support the pulley as you remove the bolt to prevent it from falling.
   Torque spec

   Idler Pulley Bolt45 Nm (33 lb-ft)
5. 5

   Remove idler pulley from engine
   Pull the idler pulley assembly straight off the mounting stud or bracket. Note the orientation and any spacers or washers behind the pulley for proper reinstallation. Clean the mounting surface with a clean rag to remove any debris or corrosion.
6. 6

   Install new idler pulley
   Position the new idler pulley onto the mounting stud or bracket, ensuring any spacers or washers are installed in the correct order as removed. Verify the pulley spins freely and is properly seated on the mounting surface before installing the bolt.
7. 7

   Install and torque idler pulley bolt
   Thread the idler pulley bolt by hand to ensure proper thread engagement. Using a torque wrench, tighten the bolt to 45.0 Nm (33.0 lb-ft). Verify the pulley still spins freely after torquing and has no excessive play or wobble.
   Torque spec

   Idler Pulley Bolt45 Nm (33 lb-ft)
8. 8

   Reinstall serpentine belt
   Following the belt routing diagram (or your reference photo), route the serpentine belt around all pulleys except one (typically the alternator or idler). Ensure the belt ribs are properly seated in all grooved pulleys. Using the 3/8" drive tool, rotate the tensioner clockwise again and slip the belt onto the final pulley. Carefully release the tensioner to apply proper tension to the belt.
9. 9

   Verify belt installation and alignment
   Visually inspect that the serpentine belt is properly seated on all pulleys with ribs fully engaged in grooved pulleys. The belt should run straight across all pulleys without misalignment. Check that the belt is not twisted anywhere in the routing path.
10. 10

    Reconnect battery and test operation
    Reconnect the negative battery cable. Start the engine and observe the accessory drive system for proper operation. Listen for any unusual noises such as squealing or chirping. Watch the belt and new idler pulley during operation to ensure smooth rotation without wobble or vibration. Allow engine to run for 2-3 minutes, then shut off and recheck belt alignment.

Reassembly

1. Ensure serpentine belt is properly routed and seated on all pulleys before starting engine
2. Double-check that idler pulley bolt is torqued to specification and pulley rotates freely
3. Verify negative battery cable is securely reconnected

Verification

• Start engine and listen for smooth, quiet operation with no squealing or grinding noises
• Visually confirm serpentine belt tracks properly on all pulleys without slipping or misalignment
• Verify new idler pulley rotates smoothly without wobble or excessive noise
• Check that all accessory systems (alternator, A/C, power steering) operate normally

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