Serpentine Belt Tensioner

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

Warnings

Tools required

Parts

• Serpentine belt tensioner assembly × 1 — Use OEM Ford specification
• Serpentine belt × 1 — Replace if worn or contaminated

Preparation

1. Ensure engine is completely cool to the touch
2. Disconnect negative battery cable and secure away from terminal
3. Remove engine cover by pulling upward on clip points (if equipped)
4. Photograph serpentine belt routing from multiple angles or reference underhood decal
5. Verify adequate overhead clearance and lighting to access front of engine

Procedure

1. 1

   Remove engine air intake components
   Loosen clamp at throttle body and disconnect air intake tube. Remove complete air filter housing assembly by releasing clips and lifting upward. This provides necessary access to the tensioner area on the passenger side of the engine.
2. 2

   Locate and inspect tensioner
   Identify the serpentine belt tensioner on the lower passenger side of the engine block. Inspect the tensioner arm for smooth operation and check the pulley for roughness, wobble, or noise by spinning it by hand. Note the direction of tensioner rotation needed for belt removal (counterclockwise).
3. 3

   Release belt tension
   Insert a 3/8 inch breaker bar into the square 3/8 inch hole on the tensioner arm. Rotate the tensioner counterclockwise to release tension on the belt. The tensioner requires significant force to compress. Hold the tensioner in the released position.
   ⚠Maintain firm control of the breaker bar. The tensioner spring has high force and can snap back suddenly if the tool slips.
4. 4

   Remove serpentine belt
   While holding the tensioner in the released position, slip the serpentine belt off the alternator pulley or any accessible pulley. Slowly release the tensioner back to its resting position. Remove the belt completely from all pulleys, noting the routing pattern as you remove it.
5. 5

   Remove tensioner mounting bolt
   Using a 15mm socket and ratchet, remove the single bolt securing the tensioner to the engine block. The bolt is accessed from above on the passenger side. Support the tensioner as you remove the bolt to prevent it from dropping.
   Torque spec

   Belt Tensioner Bolt24 Nm (18 lb-ft)
6. 6

   Remove tensioner assembly
   Lift the tensioner assembly away from the engine block. Maneuver it past any obstructing hoses or wiring. Inspect the mounting surface on the engine block for debris or damage. Clean the mounting surface with a clean rag if necessary.
7. 7

   Inspect and prepare new tensioner
   Compare the new tensioner to the old unit to verify correct replacement part. Check that the new tensioner pulley rotates smoothly and the arm moves freely through its range of motion. Verify the mounting bolt hole is clean and threads are undamaged.
8. 8

   Install new tensioner
   Position the new tensioner assembly onto the engine block mounting point. Align the mounting hole carefully. Start the tensioner bolt by hand, threading it in several turns to ensure proper thread engagement before using tools.
9. 9

   Torque tensioner bolt
   Using a torque wrench with 15mm socket, tighten the tensioner mounting bolt to specification. Ensure the tensioner is properly seated against the engine block before final torque. Verify the tensioner arm moves freely after bolt is torqued.
   ⚠The tensioner bolt is a critical fastener. Use a calibrated torque wrench and tighten to exactly 55 Nm (41 lb-ft). Do not overtighten.
   Torque spec

   Belt Tensioner Bolt24 Nm (18 lb-ft)
10. 10

    Route serpentine belt
    Beginning at the crankshaft pulley, route the new or existing belt around all pulleys following the routing diagram or reference photos taken during removal. Leave the alternator pulley or another accessible pulley for last. Ensure the belt is properly seated in all pulley grooves with ribs aligned before proceeding.
    ⚠Incorrect belt routing will cause immediate belt failure and potential engine damage. Verify routing matches the underhood diagram exactly.
11. 11

    Install belt onto final pulley
    Using the breaker bar, rotate the tensioner counterclockwise to release tension. While holding the tensioner, slip the belt onto the final pulley (typically alternator). Slowly release the tensioner, allowing it to apply proper tension to the belt. Remove the breaker bar.
12. 12

    Verify belt installation
    Visually inspect all pulleys to confirm the belt is properly seated in each groove with no twisted sections. The belt ribs must be fully engaged in all grooved pulleys. Manually rotate the crankshaft one complete revolution using a socket on the crankshaft bolt to verify smooth operation and proper tracking.

Reassembly

1. Reinstall air filter housing assembly and secure all clips
2. Reconnect air intake tube to throttle body and tighten clamp securely
3. Reinstall engine cover if equipped, ensuring all clips engage properly
4. Reconnect negative battery cable and tighten terminal connection

Verification

• Start the engine and allow it to idle. Listen for any unusual squealing, chirping, or rattling noises from the belt area
• Visually confirm the belt tracks properly on all pulleys without slipping or jumping
• Observe the tensioner arm for proper spring action and verify it maintains consistent tension
• Rev the engine to approximately 2000 RPM briefly and verify belt remains stable without slipping
• Recheck all fasteners for proper torque after test run
• Turn on electrical accessories (headlights, AC, radio) to load the alternator and verify no belt slip occurs

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