exhaust

Downpipe

for 2021 Ford F-150 3.5L V6 EcoBoost · 4WD

Difficulty

Advanced

Time

2.4 h

Tools

Steps

Remove and replace the downpipe assembly connecting the turbocharger outlets to the catalytic converters on the 3.5L EcoBoost engine.

Warnings

⚠️Exhaust system operates at extreme temperatures. Allow engine to cool completely (minimum 2 hours) before beginning work to prevent severe burns.

⚠️Vehicle must be securely supported on jack stands. Never work under a vehicle supported only by a floor jack.

⚠Exhaust fasteners are prone to corrosion and seizing. Apply penetrating oil 24 hours before beginning work if possible.

⚠O2 sensors are fragile. Avoid contaminating sensor element with oil, grease, or anti-seize. Apply anti-seize to threads only.

Tools required

Floor jack and jack standsEssential

Wheel chocksEssential

3/8" and 1/2" drive ratchet and socket set (metric)Essential

Torque wrench (10-60 Nm range)Essential

O2 sensor socket or 22mm wrenchEssential

Penetrating oilEssential

Wire brush

Exhaust hanger removal tool

Anti-seize compoundEssential

Pry bar

Heat gun or propane torch

Parts

Downpipe assembly × 1 — Use OEM specification or aftermarket equivalent
Exhaust flange gaskets (turbo to downpipe) × 2 — Use OEM specification
Catalytic converter flange gaskets × 1 — Use OEM specification
Exhaust flange bolts/nuts (if corroded) × 1 — M10 x 1.5 exhaust hardware

Preparation

Park vehicle on level surface and apply parking brake. Place wheel chocks behind rear wheels.
Allow exhaust system to cool completely (minimum 2 hours after operation).
Raise front of vehicle and support securely on jack stands rated for vehicle weight.
Spray all exhaust fasteners, O2 sensor threads, and hanger bolts with penetrating oil. Allow to soak minimum 30 minutes.
Disconnect negative battery terminal to prevent O2 sensor codes during removal.

Procedure

1
Remove heat shields
Locate and remove the heat shields covering the downpipe assembly. Remove all heat shield bolts and carefully set shields aside. These shields may be in multiple sections covering the turbos and downpipes.
Torque spec
Heat Shield Bolts10 Nm (7 lb-ft)
2
Disconnect oxygen sensors
Locate the oxygen sensors on both banks of the downpipe assembly. Disconnect the electrical connectors by pressing the release tabs. Using an O2 sensor socket or 22mm wrench, carefully unthread the sensors from the downpipe bungs. Turn counterclockwise and avoid bending the sensor body. Set sensors aside in a clean area.
⚠Do not allow O2 sensors to hang by their wires. Support the sensor body during removal.
Torque spec
O2 Sensor45 Nm (33 lb-ft)
3
Disconnect downpipe from catalytic converters
Move to the rear connection where the downpipe meets the catalytic converter assembly. Support the catalytic converter with a jack or stand. Remove the flange bolts connecting the downpipe outlet to the catalytic converter inlet. Note the position of any alignment tabs or orientation marks.
⚠Catalytic converter assembly is heavy. Ensure adequate support is in place before loosening final fasteners.
Torque spec
Exhaust Flange Bolts45 Nm (33 lb-ft)
4
Remove exhaust hanger connections
Locate the rubber exhaust hangers supporting the downpipe assembly. Remove the hanger bolts or carefully pry the hangers off their mounting brackets using a pry bar or exhaust hanger removal tool. Note the position of each hanger for reassembly.
Torque spec
Hanger Bolts23 Nm (17 lb-ft)
5
Disconnect downpipe from turbochargers
Access the forward connection points where the downpipe flanges connect to both turbocharger outlets. Remove the exhaust flange bolts/nuts from both driver and passenger side turbo outlets. These connections are at the bottom of each turbocharger housing.
⚠Fasteners may be severely corroded. If bolts begin to strip or break, apply heat and allow to cool before attempting removal again.
Torque spec
Exhaust Flange Bolts45 Nm (33 lb-ft)
6
Remove downpipe assembly
With all connections disconnected, carefully maneuver the downpipe assembly downward and rearward out of the vehicle. The assembly may require rotation and angling to clear the frame rails and suspension components. Have an assistant support the opposite end during removal due to weight and size.
ℹ️Downpipe assembly weighs approximately 25-35 lbs and is awkward to handle. Plan removal path before fully disconnecting.
7
Clean mating surfaces
Using a wire brush and scraper, thoroughly clean all exhaust flange mating surfaces at the turbocharger outlets and catalytic converter inlet. Remove all old gasket material, carbon buildup, and corrosion. Clean surfaces must be flat and smooth for proper sealing.
ℹ️Wear eye protection when wire brushing to prevent carbon particles from entering eyes.
8
Install new gaskets and position new downpipe
Install new exhaust flange gaskets at both turbocharger outlet connections. Position the new or replacement downpipe assembly by maneuvering it up into place, aligning the forward flanges with the turbocharger outlets first. Ensure gaskets remain properly seated during positioning.
ℹ️Do not apply anti-seize to gasket surfaces. Anti-seize is for fastener threads only.
9
Connect downpipe to turbochargers
Apply anti-seize compound to the threads of new or cleaned exhaust flange bolts. Install and hand-tighten the exhaust flange bolts at both turbocharger connections. Once all bolts are started, torque in a cross-pattern to specification.
Torque spec
Exhaust Flange Bolts45 Nm (33 lb-ft)
10
Install exhaust hangers
Reconnect the exhaust hangers to their mounting positions. Install hanger bolts and torque to specification. Ensure the downpipe assembly is properly supported and aligned before fully tightening.
Torque spec
Hanger Bolts23 Nm (17 lb-ft)
11
Connect downpipe to catalytic converters
Install new flange gasket at the catalytic converter connection point. Align the downpipe outlet flange with the catalytic converter inlet flange. Apply anti-seize to flange bolt threads, install bolts, and torque in a cross-pattern to specification.
Torque spec
Exhaust Flange Bolts45 Nm (33 lb-ft)
12
Reinstall oxygen sensors
Apply a thin coat of anti-seize compound to the threads of each oxygen sensor only (avoid getting any on the sensor element). Thread sensors by hand into their bungs on the new downpipe. Torque to specification using O2 sensor socket. Reconnect electrical connectors ensuring they click into place.
Torque spec
O2 Sensor45 Nm (33 lb-ft)
13
Reinstall heat shields
Position heat shields back over the downpipe assembly. Install and torque all heat shield bolts to specification. Ensure shields are properly seated and not contacting any moving components.
Torque spec
Heat Shield Bolts10 Nm (7 lb-ft)
14
Final inspection and lower vehicle
Perform a visual inspection of all connections, verifying all fasteners are tight and no tools or parts have been left in the engine bay. Reconnect negative battery terminal. Lower vehicle from jack stands.

Reassembly

Verify all exhaust connections are tight and properly gasketed
Ensure oxygen sensor wiring is routed away from heat sources and moving components
Check that heat shields are secure and not rattling
Confirm all exhaust hangers are properly engaged and supporting the system

Verification

Start engine and allow to idle. Listen for exhaust leaks at turbocharger and catalytic converter connections (hissing or ticking sounds indicate leaks)
Inspect all connection points for visible exhaust gas escaping while engine is running
Check for dashboard warning lights related to O2 sensors or exhaust system
Test drive vehicle and verify normal boost levels and no unusual exhaust noises
After test drive, re-inspect all connections for signs of leaks or loosening while engine is still warm