This procedure covers the replacement of the serpentine belt idler pulley on the 2011-2014 Ford F-150 with 3.5L EcoBoost engine, including belt removal and reinstallation.

Warnings

Tools required

Parts

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

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow engine to cool completely if recently operated
3. Photograph or draw the serpentine belt routing diagram before removal for reference
4. Ensure adequate lighting in engine bay for visibility

Procedure

1. 1

   Locate the idler pulley
   Open the hood and locate the idler pulley on the front of the engine. On the 3.5L EcoBoost, the idler pulley is positioned between the alternator and the belt tensioner on the driver's side of the engine bay. Identify the smooth idler pulley (not grooved) that the flat side of the belt rides on.
2. 2

   Document belt routing
   Take a clear photograph of the serpentine belt routing with your phone, ensuring all pulleys are visible. This is critical for proper belt reinstallation. If a belt routing diagram is present on a decal under the hood, photograph that as well for reference.
3. 3

   Release belt tension
   Locate the belt tensioner pulley (spring-loaded pulley with a 3/8" square drive socket hole). Insert a 3/8" drive ratchet or breaker bar into the square hole on the tensioner. Rotate the tensioner clockwise to release tension on the belt. The tensioner will move significantly when rotated.
   ⚠Maintain firm control of the tensioner tool as the spring tension is strong and can snap back forcefully
4. 4

   Remove serpentine belt
   While holding the tensioner in the released position, slip the serpentine belt off one of the pulleys (typically easiest from the alternator). Slowly release the tensioner back to its resting position. Remove the belt completely from all pulleys and from the engine bay.
5. 5

   Remove idler pulley bolt
   Using the appropriate metric socket, remove the center bolt securing the idler pulley to its bracket. The bolt threads into a mounting boss on the engine front cover. Remove the bolt completely and set aside.
   Torque spec

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

   Remove idler pulley
   Pull the idler pulley straight off the mounting stud or boss. If the pulley has a spacer or washer behind it, note its position and remove it as well. Inspect the mounting surface for debris or damage.
7. 7

   Inspect and clean mounting surface
   Clean the idler pulley mounting boss on the engine front cover with a clean rag. Inspect for any damage or excessive wear. Check that the mounting threads are clean and undamaged.
8. 8

   Install new idler pulley
   Position the new idler pulley onto the mounting boss, ensuring any spacers or washers are installed in the correct order as removed. The pulley should spin freely by hand. Insert the idler pulley bolt and thread it in by hand to prevent cross-threading.
9. 9

   Torque idler pulley bolt
   Using a torque wrench, tighten the idler pulley bolt to the specified torque of 45.0 Nm (33.0 lb-ft). After torquing, verify the pulley still rotates smoothly without binding or excessive play.
   Torque spec

   Idler Pulley Bolt45 Nm (33 lb-ft)
10. 10

    Reinstall serpentine belt
    Route the serpentine belt around all pulleys according to your photograph or the routing diagram, leaving the tensioner pulley for last. Ensure the belt is properly seated in all pulley grooves and that the smooth back side of the belt contacts the idler pulley and tensioner.
11. 11

    Engage belt on tensioner
    Insert the 3/8" drive tool into the tensioner and rotate clockwise to relieve tension. Slip the belt over the tensioner pulley, ensuring it is properly seated in the grooves. Slowly release the tensioner to apply proper tension to the belt.
    ⚠Control the tensioner release to prevent the tool from slipping and causing injury
12. 12

    Verify belt installation
    Visually inspect the entire belt path to confirm the belt is properly seated on all pulleys with no twists or misalignment. The ribbed side should contact all grooved pulleys, and the smooth back should contact the idler and tensioner. Manually rotate the engine one full revolution by turning the crankshaft pulley clockwise and verify the belt tracks correctly on all pulleys.

Reassembly

1. Double-check that the serpentine belt is properly routed and seated on all pulleys
2. Verify the idler pulley rotates freely without noise or binding
3. Ensure no tools or parts have been left in the engine bay

Verification

• Start the engine and listen for any unusual squealing, chirping, or rattling noises from the belt area
• Observe the belt operation for the first few seconds to ensure proper tracking on all pulleys
• With engine running, verify the idler pulley is rotating smoothly without wobble or vibration
• Turn the steering wheel lock-to-lock and activate accessories (A/C, defroster) to verify belt operates properly under load
• Re-inspect belt routing after engine reaches operating temperature to confirm no slipping has occurred

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