This procedure covers replacement of the downpipe assembly on the 3.5L EcoBoost engine, connecting the turbocharger outlets to the catalytic converters.

Warnings

Tools required

Parts

• Downpipe gasket set × 1 — Use OEM specification
• Exhaust flange hardware kit × 1 — Use OEM specification
• Oxygen sensor (if damaged) × 2 — 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. Spray all exhaust flange bolts, oxygen sensors, and hanger bolts with penetrating oil and allow to soak
5. Raise front of vehicle and support on jack stands at frame rails
6. Remove engine undervershield/splash shield if equipped

Procedure

1. 1

   Disconnect oxygen sensors
   Locate the upstream oxygen sensors on each downpipe. Disconnect the electrical connectors by pressing the release tab and pulling straight out. Using an oxygen sensor socket or 22mm deep socket, carefully remove both upstream oxygen sensors. Turn counterclockwise and apply steady pressure - do not force if seized. If sensors will not release easily, apply heat to the bung area and retry.
2. 2

   Remove heat shields
   Remove the heat shields covering the downpipes and turbocharger area. Remove all heat shield mounting bolts. There are typically multiple shields that may overlap. Keep track of shield positions for reassembly.
   Torque spec

   Heat Shield Bolts10 Nm (7 lb-ft)
3. 3

   Disconnect downpipe from catalytic converter
   Locate the flange connection where the downpipes connect to the catalytic converters (mid-pipe assembly). Remove the flange bolts connecting these components. There are typically 3 bolts per side at this connection point. Support the downpipe assembly as you remove the final bolts.
   ⚠These flange bolts are frequently seized due to heat cycling. Apply additional penetrating oil and allow to soak if resistance is encountered.
   Torque spec

   Exhaust Flange Bolts45 Nm (33 lb-ft)
4. 4

   Remove exhaust hanger supports
   Locate the rubber exhaust hangers supporting the downpipe assembly. Using a pry bar if necessary, carefully separate the exhaust hanger mounts from the rubber isolators. There are typically 1-2 hanger points on the downpipe assembly. Remove any hanger bolts that secure brackets to the chassis.
   Torque spec

   Hanger Bolts23 Nm (17 lb-ft)
5. 5

   Disconnect downpipes from turbocharger outlets
   Access the turbocharger outlet flanges at the top of the downpipe assembly. Remove the exhaust flange bolts connecting each downpipe to its respective turbocharger outlet (driver side and passenger side). There are typically 3 bolts per turbo outlet. Note the presence of spring-loaded studs on some applications.
   ⚠️Turbocharger components may retain heat longer than other exhaust parts. Verify cool to touch before proceeding.
   Torque spec

   Exhaust Flange Bolts45 Nm (33 lb-ft)
6. 6

   Remove downpipe assembly
   With all fasteners removed, carefully maneuver the downpipe assembly downward and out from the vehicle. The assembly is heavy (approximately 30-40 lbs) and awkward. You may need to rotate and angle the assembly to clear the crossmember and steering components. Inspect all mounting points for damage during removal.
7. 7

   Clean and inspect mounting surfaces
   Using a wire brush and scraper, thoroughly clean all gasket surfaces at the turbocharger outlets and catalytic converter flanges. Remove all old gasket material and carbon buildup. Inspect turbocharger outlet flanges and catalytic converter inlet flanges for warping, cracks, or damage. Check all studs and threaded holes for damage.
   ℹ️Warped or damaged flanges will cause exhaust leaks even with new gaskets. Replace damaged components before proceeding.
8. 8

   Prepare new downpipe and oxygen sensors
   If installing new oxygen sensors, apply a small amount of anti-seize compound to the threads only - do not get anti-seize on the sensor tip. Install new gaskets on the downpipe flanges. Apply anti-seize to all exhaust flange bolt threads. Position the new or cleaned downpipe assembly for installation.
9. 9

   Install downpipe to turbocharger outlets
   Carefully maneuver the downpipe assembly into position and align with the turbocharger outlet flanges. Install exhaust flange bolts at both turbocharger outlets, starting all bolts hand-tight before torquing any. Apply anti-seize to bolt threads. Once all bolts are started, torque in a cross-pattern to specification.
   ⚠Ensure gaskets remain properly seated during alignment. Misaligned gaskets will cause exhaust leaks.
   Torque spec

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

    Connect downpipe to catalytic converter
    Align the downpipe outlet flanges with the catalytic converter inlet flanges. Install new gaskets if not already in place. Install all flange bolts hand-tight, then torque in a cross-pattern to specification. Verify proper gasket seating before final torque.
    Torque spec

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

    Install exhaust hangers
    Reconnect the exhaust hanger brackets to the rubber isolators on the chassis. Install and torque any hanger bolts to specification. Ensure the exhaust system hangs properly without binding or excessive tension on any connection point.
    Torque spec

    Hanger Bolts23 Nm (17 lb-ft)
12. 12

    Install oxygen sensors
    Thread the upstream oxygen sensors into their bungs by hand to avoid cross-threading. Once hand-tight, torque to specification using an oxygen sensor socket. Do not over-torque as this can damage the sensor housing. Reconnect the electrical connectors ensuring they click into place securely.
    ⚠Anti-seize must be applied to threads only. Contamination of the sensor element will cause false readings and check engine lights.
    Torque spec

    O2 Sensor45 Nm (33 lb-ft)
13. 13

    Reinstall heat shields
    Reinstall all heat shields in their original positions. Install and torque all heat shield bolts to specification. Ensure heat shields do not contact moving components or create vibration points.
    Torque spec

    Heat Shield Bolts10 Nm (7 lb-ft)

Reassembly

1. Reinstall engine splash shield/undershield if equipped
2. Lower vehicle from jack stands
3. Verify all tools and parts have been removed from under vehicle
4. Double-check all electrical connectors are properly seated

Verification

• Start engine and listen for exhaust leaks at all flange connections - a hissing sound indicates a leak
• Allow engine to reach operating temperature and recheck for leaks
• Inspect all connections visually for signs of exhaust gas escape (soot marks)
• Test drive vehicle and verify no exhaust odors in cabin
• Scan for diagnostic trouble codes - verify no oxygen sensor or exhaust system codes are present
• After 50-100 miles of driving, re-inspect all flange connections for looseness or leaks

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