This procedure covers the removal and replacement of the air injection check valve on the 3.5L EcoBoost engine, which prevents exhaust gases from entering the secondary air injection system.

Warnings

Tools required

Parts

• Air injection check valve × 1 — Use OEM specification
• Check valve mounting gasket × 1 — Use OEM specification
• Air injection tube gaskets × 2 — Use OEM specification

Preparation

1. Ensure engine has been off for at least 2 hours to allow exhaust system to cool completely
2. Disconnect negative battery cable to prevent electrical issues while working near sensors
3. Raise and support vehicle on jack stands if accessing from underneath for better visibility
4. Apply penetrating oil to check valve mounting bolts and air injection tube connections if visible corrosion is present

Procedure

1. 1

   Access the air injection check valve
   The check valve is located on the passenger side of the engine bay near the turbocharger. Remove the engine cover by pulling upward on the front and rear to release the grommets. Set aside the cover. Identify the check valve assembly between the secondary air injection pump and the exhaust manifold.
2. 2

   Disconnect the air injection pump supply line
   Locate the air supply line running from the secondary air pump to the check valve inlet. Loosen the clamp or connection at the check valve using a 10mm socket. Carefully pull the air supply hose from the check valve inlet, being careful not to damage the hose end. If stuck, gently twist while pulling.
3. 3

   Remove electrical connections if present
   Some check valve configurations include temperature sensors or pressure sensors. If electrical connectors are present on or near the check valve, press the release tab and carefully disconnect them. Note the routing of wiring harnesses for reinstallation.
4. 4

   Disconnect the exhaust manifold outlet tube
   The check valve outlet connects to the exhaust manifold via a tube or pipe. Locate the flange connection bolts at the exhaust manifold. Remove the flange bolts using a 13mm socket. There are typically 2 bolts per connection. Separate the tube from the manifold and check valve, noting the position of any gaskets.
   Torque spec

   Exhaust Flange Bolts45 Nm (33 lb-ft)
5. 5

   Remove check valve mounting bolts
   Locate the mounting bolts that secure the check valve to its bracket or mounting point on the engine. These are typically 10mm bolts. Remove all mounting bolts while supporting the check valve assembly to prevent it from falling.
   Torque spec

   Mounting Bolts31 Nm (23 lb-ft)
6. 6

   Remove the check valve assembly
   Carefully maneuver the check valve out of the engine bay. The assembly may need to be tilted or rotated to clear surrounding components like the turbocharger heat shield, wiring harnesses, and coolant lines. Take note of the orientation and position for installation of the new valve.
7. 7

   Inspect mounting surfaces and connections
   Examine all mounting surfaces, flange connections, and gasket sealing areas for damage, warping, or excessive corrosion. Clean all mounting surfaces with a wire brush or scraper. Check the air supply hose for cracks or deterioration. Replace any damaged components before installing the new check valve.
8. 8

   Prepare the new check valve
   Unpack the new check valve and verify it matches the old unit. Install new gaskets on both the inlet and outlet connections. Do not reuse old gaskets. Ensure the check valve arrow or flow direction marking points toward the exhaust manifold (outlet side).
9. 9

   Install the new check valve
   Position the new check valve into the mounting location, ensuring proper orientation with flow direction toward the exhaust. Start all mounting bolts by hand to ensure proper thread engagement. Tighten the mounting bolts to specification using a torque wrench.
   Torque spec

   Mounting Bolts31 Nm (23 lb-ft)
10. 10

    Connect the exhaust outlet tube
    Install new gaskets at the exhaust manifold flange connection. Position the outlet tube between the check valve and exhaust manifold. Start the flange bolts by hand. Apply anti-seize compound to the bolt threads as specified. Torque the exhaust flange bolts to specification in a cross-pattern to ensure even gasket compression.
    Torque spec

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

    Reconnect air supply and electrical connections
    Attach the air supply hose to the check valve inlet, ensuring it is fully seated. Tighten the hose clamp securely. Reconnect any electrical connectors that were removed, ensuring they click into place. Verify all connections are secure and properly routed away from hot exhaust components.
12. 12

    Final inspection and battery reconnection
    Double-check all connections, mounting bolts, and hose clamps for proper torque and security. Ensure no tools or parts have been left in the engine bay. Reinstall the engine cover by aligning the grommets and pressing down firmly. Reconnect the negative battery cable.

Reassembly

1. Ensure all exhaust connections are properly torqued with anti-seize applied to prevent future seizure
2. Verify the check valve flow direction arrow points toward the exhaust manifold
3. Confirm all electrical connectors are fully seated and locked
4. Route all hoses and wiring away from hot exhaust components and moving parts

Verification

• Start the engine and listen for any unusual hissing or air leaks from the check valve area
• Allow the engine to reach operating temperature and verify no exhaust leaks are present at flange connections
• Use a scan tool to check for any secondary air injection system fault codes
• Verify the secondary air injection system operates correctly during cold start (you may hear the air pump running for 1-2 minutes)
• Confirm no check engine light illuminates after completing a full drive cycle

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