This procedure covers the replacement of the flex pipe section in the exhaust system on a 2011-2014 Ford F-150 with the 5.0L Coyote V8 engine.

Warnings

Tools required

Parts

• Flex pipe assembly with flanges × 1 — Use OEM specification or direct-fit aftermarket
• Exhaust flange gaskets × 2 — 3-inch donut gasket
• Exhaust flange bolts and nuts × 4 — M10 x 1.5 x 35mm
• Exhaust hanger isolators (rubber) × 2 — Replace if deteriorated

Preparation

1. Park vehicle on level surface and engage parking brake
2. Place wheel chocks behind rear wheels
3. Allow exhaust system to cool completely (minimum 2 hours after last operation)
4. Raise front of vehicle and support securely on jack stands at frame rails
5. Spray all exhaust flange bolts, clamps, and O2 sensor threads with penetrating oil
6. Locate flex pipe assembly between Y-pipe and catalytic converters

Procedure

1. 1

   Disconnect upstream oxygen sensor
   Locate the upstream O2 sensor on or near the flex pipe section. Disconnect the electrical connector by pressing the release tab. Using the O2 sensor socket, carefully unthread the sensor from the exhaust pipe. If sensor is seized, apply heat carefully with a propane torch while turning. Store sensor safely to prevent damage to the tip.
   ⚠O2 sensors are fragile. Never use excessive force or standard sockets that may damage the hex or wiring.
2. 2

   Support exhaust system
   Position a floor jack with a block of wood under the exhaust system just behind the flex pipe section to support the weight of the downstream components during removal. Raise jack until it just contacts the pipe but does not lift it.
3. 3

   Remove upstream flange connection
   Remove the two nuts and bolts connecting the flex pipe to the Y-pipe flange at the front connection. If bolts spin, use a backup wrench on the bolt head while turning the nut. Remove and discard the old flange gasket. Clean the flange mating surface with a wire brush.
   ℹ️Spray bolts again with penetrating oil if they resist turning. Rusted bolts may require cutting with a reciprocating saw.
4. 4

   Remove downstream flange connection
   Remove the two nuts and bolts connecting the flex pipe to the catalytic converter flange at the rear connection. Remove and discard the old flange gasket. Clean the flange mating surface thoroughly with a wire brush to ensure proper seal.
5. 5

   Disconnect exhaust hangers
   Locate the rubber exhaust hanger isolators supporting the flex pipe section. Use a prying tool or screwdriver to carefully work the metal hooks out of the rubber isolators. You may need to push up on the pipe or pull down on the hanger to create slack. Inspect rubber isolators for tears or deterioration and replace if necessary.
6. 6

   Remove flex pipe assembly
   Carefully lower the jack supporting the exhaust slightly while guiding the flex pipe assembly down and out from under the vehicle. Maneuver the pipe past the transmission crossmember and driveshaft. Take note of the orientation and routing for installation of the new pipe.
7. 7

   Prepare new flex pipe
   Unpack the new flex pipe assembly and verify it matches the original in length, flange orientation, and sensor bung location. Install new flange gaskets on both flanges of the new flex pipe. Apply a thin coat of anti-seize compound to the O2 sensor threads (avoid contaminating the sensor tip).
8. 8

   Install flex pipe assembly
   Maneuver the new flex pipe into position under the vehicle, routing it past the crossmember and driveshaft. Align the front flange with the Y-pipe and the rear flange with the catalytic converter inlet. Hook the pipe hangers into the rubber isolators. Raise the jack to support the assembly while aligning.
9. 9

   Install upstream flange connection
   Install the two new flange bolts and nuts at the Y-pipe connection. Start both bolts before tightening either. Tighten the flange bolts in a crisscross pattern to the specified torque to ensure even loading and proper seal.
   Torque spec

   Flange Bolts45 Nm (33 lb-ft)
10. 10

    Install downstream flange connection
    Install the two new flange bolts and nuts at the catalytic converter connection. Start both bolts before tightening either. Tighten the flange bolts in a crisscross pattern to the specified torque.
    Torque spec

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

    Reinstall oxygen sensor
    Thread the O2 sensor into the flex pipe bung by hand to avoid cross-threading. Once hand-tight, use the O2 sensor socket and torque wrench to tighten to specification. Reconnect the electrical connector and ensure the wiring is routed away from hot exhaust components with adequate clearance.
    ⚠Do not over-torque the O2 sensor as this can damage the threads in the exhaust pipe. Use a torque wrench and the specified value.
    Torque spec

    O2 Sensor59 Nm (44 lb-ft)
12. 12

    Final adjustment and inspection
    Remove the supporting jack from under the exhaust. Verify all exhaust hangers are properly seated in their isolators. Check that there is adequate clearance between the exhaust and all chassis components, driveshaft, and fuel lines. Ensure no contact points exist that could cause rattles or damage.

Reassembly

1. Double-check all flange bolts are torqued to specification
2. Verify O2 sensor electrical connector is fully seated and locked
3. Ensure exhaust hangers are properly engaged and pipe has proper clearance throughout its length
4. Lower vehicle from jack stands

Verification

• Start engine and listen for exhaust leaks at both flange connections while engine is cold
• With engine at idle, visually inspect all connections for signs of exhaust gas leakage
• Allow engine to reach operating temperature and re-check for leaks under load
• Test drive vehicle and listen for unusual exhaust noises, rattles, or vibrations
• After test drive, re-inspect all connections while exhaust is hot for any signs of leakage
• Verify no exhaust odors enter the cabin during operation

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