This procedure covers removal and installation of the serpentine belt on the 3.5L V6 EcoBoost engine, including tensioner operation and belt routing verification.

Warnings

Tools required

Parts

• Serpentine belt × 1 — Use OEM specification or Gates K061098

Preparation

1. Ensure engine is completely cool to the touch
2. Park vehicle on level surface and engage parking brake
3. Photograph or sketch the serpentine belt routing before removal for reference
4. Verify belt routing diagram is visible on radiator support or underside of hood

Procedure

1. 1

   Access the serpentine belt
   Open the hood and secure it in the open position. Locate the serpentine belt at the front of the engine. On the 3.5L EcoBoost, the belt drives the alternator, water pump, power steering pump, and A/C compressor. The belt tensioner is located on the passenger side of the engine block.
2. 2

   Document belt routing
   Before removal, take a clear photograph of the belt routing path around all pulleys. If the belt routing diagram decal is missing or unclear, sketch the routing pattern. The belt follows a specific serpentine pattern around the crankshaft pulley, alternator, A/C compressor, idler pulley, water pump, and tensioner pulley.
3. 3

   Relieve belt tension
   Using a 3/8" drive ratchet or breaker bar, insert the tool into the square 3/8" drive hole in the belt tensioner arm. Rotate the tensioner clockwise (toward the passenger side) to relieve tension on the belt. The tensioner will move approximately 90 degrees. This is a spring-loaded automatic tensioner, so maintain firm control throughout the movement.
   ⚠Do not allow the tensioner to snap back suddenly. Control the release to prevent damage to the tensioner mechanism.
4. 4

   Remove serpentine belt
   While holding the tensioner in the relaxed position, slide the belt off the nearest pulley (typically the alternator or tensioner pulley). Once the belt is free from one pulley, slowly release the tensioner and allow it to return to its resting position. Remove the belt from the remaining pulleys and extract it from the engine compartment.
5. 5

   Inspect pulleys and tensioner
   With the belt removed, manually spin each pulley to check for smooth rotation. Listen for bearing noise or grinding. Check that all pulleys rotate in the same plane without wobbling. Inspect the tensioner pulley for smooth operation and verify the tensioner arm moves freely and returns to its rest position with adequate spring tension. Check the tensioner mounting bolt for tightness.
   Torque spec

   Belt Tensioner Bolt55 Nm (41 lb-ft)
6. 6

   Inspect idler pulley
   Check the idler pulley bearing for smooth operation and proper alignment. Verify the idler pulley bolt is secure. If the pulley shows any resistance, noise, or wobble, it should be replaced before installing the new belt.
   Torque spec

   Idler Pulley Bolt45 Nm (33 lb-ft)
7. 7

   Route new serpentine belt
   Begin installing the new belt by routing it around all pulleys EXCEPT the tensioner pulley, following your photograph or the routing diagram. Start at the crankshaft pulley and work your way around the accessory pulleys. Ensure the belt ribs are properly seated in each pulley groove. The smooth back side of the belt should contact the tensioner pulley, while the ribbed side contacts all other pulleys.
8. 8

   Install belt on tensioner
   Using the 3/8" drive ratchet, rotate the tensioner clockwise again to create slack. Route the belt over or under the tensioner pulley (per routing diagram), ensuring proper rib engagement. Slowly release the tensioner, allowing it to apply proper tension to the belt. Verify the belt is fully seated in all pulley grooves.
9. 9

   Verify belt alignment and seating
   Visually inspect all pulleys to confirm the belt is properly centered on each pulley and fully seated in the grooves. The belt should not be riding on the edge of any pulley. Check that the belt follows the exact routing pattern from your reference diagram, with the ribbed side contacting the correct pulleys.
10. 10

    Test belt operation
    Manually rotate the crankshaft pulley clockwise (viewed from front) two complete revolutions using a socket on the crankshaft bolt. Observe the belt to ensure it tracks properly on all pulleys without jumping or misalignment. Verify the belt maintains proper position throughout the rotation.

Reassembly

1. No disassembly of components was required for this procedure
2. Ensure all tools are removed from engine compartment before starting engine

Verification

• Start the engine and observe belt operation for 30-60 seconds. Belt should run smoothly without squealing, chirping, or slipping
• Check that belt remains centered on all pulleys during engine operation
• Listen for any unusual noises from belt or pulleys that might indicate misalignment or defective components
• Turn on electrical accessories (A/C, headlights, radio) to load the alternator and verify belt handles the increased load without slipping
• After initial test run, shut off engine and perform final visual inspection to confirm belt remains properly seated

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