This procedure covers the removal and replacement of the serpentine belt that drives the alternator and other accessories on the 3.5L EcoBoost V6 engine.

Warnings

Tools required

Parts

• Serpentine belt × 1 — Motorcraft 8PK2525 or equivalent

Preparation

1. Park vehicle on level ground and engage parking brake
2. Allow engine to cool completely (minimum 30 minutes after shutdown)
3. Open hood and secure with prop rod
4. Take a photo of the belt routing path before removal for reference, or locate the belt routing diagram on the radiator shroud or hood underside

Procedure

1. 1

   Locate belt tensioner
   From the front of the vehicle, identify the automatic belt tensioner on the passenger side of the engine. The tensioner is a spring-loaded pulley assembly with a 3/8 inch square drive socket in the center of the tensioner arm.
2. 2

   Release belt tension
   Insert a 3/8 inch drive ratchet or breaker bar into the square drive hole on the tensioner arm. Rotate the tensioner clockwise (toward the passenger side fender) to relieve tension on the belt. The tensioner will move approximately 90 degrees.
3. 3

   Remove serpentine belt
   While holding tension released, slip the belt off the alternator pulley or any other easily accessible pulley. Carefully release the tensioner back to its resting position. Remove the belt completely from all pulleys, noting its routing path.
4. 4

   Inspect components
   With the belt removed, manually rotate each pulley to check for rough bearings, excessive play, or noise. Inspect the alternator pulley, idler pulleys, tensioner pulley, water pump pulley, crankshaft pulley, and A/C compressor pulley. Replace any components showing wear.
5. 5

   Inspect old belt
   Examine the removed belt for cracks, glazing, chunks missing from ribs, or excessive wear. Check for oil or coolant contamination which indicates a leak that must be addressed. Belt should be replaced if any damage is present or if at recommended service interval.
6. 6

   Route new belt
   Using your reference photo or the belt routing diagram, route the new serpentine belt around all pulleys EXCEPT the alternator pulley. Ensure the ribbed side of the belt contacts all grooved pulleys. The backside (smooth side) typically contacts the tensioner pulley and one idler pulley on this engine.
7. 7

   Install belt on alternator
   Insert the 3/8 inch drive ratchet into the tensioner and rotate clockwise to relieve tension. Slip the belt onto the alternator pulley while holding the tensioner. Carefully release the tensioner to apply proper tension to the belt. Verify the belt is properly seated in all pulley grooves.
8. 8

   Verify belt alignment
   Visually inspect that the belt is correctly seated in all pulley grooves along its entire path. The belt should not be twisted and should run straight across each pulley. Check that no portion of the belt is riding on pulley edges or outside the grooves.

Reassembly

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

Verification

• Start the engine and observe belt operation for 30 seconds, listening for unusual noises such as squealing or chirping
• Verify the belt runs smoothly without slipping, hopping, or vibrating excessively
• Check that all accessories are functioning properly (alternator charging, A/C compressor engaging if commanded, power steering assist responsive)
• Shut off engine and perform final visual inspection to confirm belt remains properly seated on all pulleys

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