This procedure covers the removal and replacement of the exhaust flex pipe on a 2015-2020 Ford F-150 with the 3.5L EcoBoost V6 engine.

Warnings

Tools required

Parts

• Flex pipe assembly × 1 — Use OEM specification or quality aftermarket
• Exhaust flange gasket × 2 — Use OEM specification
• Oxygen sensor (if damaged) × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface and apply parking brake
2. Place wheel chocks behind rear wheels
3. Allow exhaust system to cool completely (minimum 2 hours after engine operation)
4. Raise front of vehicle with floor jack and secure with jack stands under frame rails
5. Spray all exhaust fasteners with penetrating oil and allow to soak for 15-20 minutes

Procedure

1. 1

   Locate flex pipe assembly
   Position yourself under the vehicle and locate the flex pipe assembly. On the 3.5L EcoBoost, the flex pipe is positioned after the dual turbocharger downpipes merge and before the catalytic converters. Identify the upstream and downstream flange connections and any oxygen sensor wiring.
2. 2

   Disconnect oxygen sensor (if equipped on flex pipe)
   Locate the oxygen sensor electrical connector and press the release tab to disconnect. If the oxygen sensor is threaded into the flex pipe section being replaced, use a 22mm oxygen sensor socket to carefully remove it. Apply anti-seize to threads upon reinstallation.
   Torque spec

   O2 Sensor55 Nm (40 lb-ft)
3. 3

   Support exhaust system
   Position a jack stand or transmission jack under the catalytic converter section to support the weight of the downstream exhaust once the flex pipe is disconnected. Adjust height to prevent excessive strain on exhaust hangers.
4. 4

   Remove upstream flange bolts
   Using a 15mm socket, remove the bolts securing the upstream flange connection between the downpipe and flex pipe. There are typically 3 bolts in a triangular pattern. Work bolts back and forth if seized. Remove and discard the old exhaust gasket.
   ⚠Flange bolts may break if severely corroded. Have replacement hardware available if needed.
5. 5

   Remove downstream flange bolts
   Using a 15mm socket, remove the bolts securing the downstream flange connection between the flex pipe and catalytic converter section. There are typically 3 bolts in a triangular pattern. Remove and discard the old exhaust gasket.
   ⚠Support the flex pipe as you remove the final bolts to prevent it from falling.
6. 6

   Remove exhaust hanger connections
   If the flex pipe assembly has rubber exhaust hangers attached, use an exhaust hanger removal tool or carefully pry the rubber isolators off the hanger brackets. Note the orientation and position of hangers for reinstallation.
7. 7

   Remove flex pipe assembly
   Carefully maneuver the flex pipe assembly down and out from under the vehicle. The dual downpipe configuration may require angling the component to clear surrounding parts. Inspect the removed flex pipe for damage, cracks in the flex section, or failed welds.
8. 8

   Clean flange surfaces
   Use a wire brush to thoroughly clean both the upstream and downstream exhaust flange surfaces. Remove all old gasket material, carbon deposits, and corrosion to ensure proper sealing with new gaskets. Inspect flange faces for warping or damage.
9. 9

   Install new flex pipe assembly
   Position new exhaust flange gaskets on both upstream and downstream connections. Carefully maneuver the new flex pipe into position, aligning the flanges. Reconnect any exhaust hanger isolators to their mounting brackets. Thread flange bolts finger-tight to hold the assembly in place.
   ℹ️Ensure the flex pipe is oriented correctly with proper clearance from chassis components and heat shields.
10. 10

    Torque upstream flange bolts
    Using a torque wrench, tighten the upstream flange bolts in a star or cross pattern to ensure even gasket compression and proper sealing. This prevents exhaust leaks at the connection.
    Torque spec

    Flange Bolts45 Nm (33 lb-ft)
11. 11

    Torque downstream flange bolts
    Using a torque wrench, tighten the downstream flange bolts in a star or cross pattern to ensure even gasket compression and proper sealing.
    Torque spec

    Flange Bolts45 Nm (33 lb-ft)
12. 12

    Reinstall oxygen sensor
    If the oxygen sensor was removed, apply a thin coat of anti-seize compound to the threads (avoiding the sensor tip). Thread the sensor into the new flex pipe by hand, then tighten to specification using an oxygen sensor socket. Reconnect the electrical connector until it clicks.
    Torque spec

    O2 Sensor55 Nm (40 lb-ft)
13. 13

    Remove exhaust support and lower vehicle
    Remove the jack stand or transmission jack supporting the exhaust system. Verify all exhaust hangers are properly seated and the system hangs evenly with proper clearance. Lower the vehicle from the jack stands and remove all equipment from under the vehicle.

Reassembly

1. Verify all exhaust flange bolts are torqued to specification
2. Confirm oxygen sensor electrical connector is fully seated
3. Check that all exhaust hangers are properly installed and the system has adequate clearance from chassis, drivetrain, and heat shields

Verification

• Start the engine and listen for any exhaust leaks at the flex pipe connections while the system is cold
• Allow engine to reach operating temperature and re-inspect all connections for leaks
• Check for exhaust smell in cabin which would indicate a leak
• Verify no exhaust rattle or contact with chassis components during engine operation
• Clear any diagnostic codes if oxygen sensor was disconnected and verify no new codes are present

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