Air Injection Check Valve

This procedure covers the removal and replacement of the air injection check valve on the 2015-2020 Ford F-150 3.5L EcoBoost engine, which prevents backflow in the secondary air injection system.

Warnings

Tools required

Parts

• Air injection check valve × 1 — Use OEM specification
• Check valve gasket × 1 — Use OEM specification
• Air injection hose clamps × 2 — Replace if damaged

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow engine and exhaust system to cool completely (minimum 2 hours)
3. Disconnect negative battery terminal to prevent accidental secondary air pump activation
4. Locate the air injection check valve near the exhaust manifold on the driver's side of the engine
5. For improved access, raise and support vehicle on jack stands if accessing from below

Procedure

1. 1

   Remove engine cover
   Remove the plastic engine cover by lifting upward to release the retaining grommets. Set aside in a clean area.
2. 2

   Access check valve area
   Locate the air injection check valve assembly on the driver's side of the engine bay, positioned between the secondary air pump and the exhaust manifold. Remove any heat shields or covers blocking access to the check valve mounting area.
   Torque spec

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

   Disconnect inlet air hose
   Loosen the hose clamp securing the inlet air hose from the secondary air pump to the check valve. Use pliers to compress the clamp and slide it back along the hose. Carefully twist and pull the hose from the check valve inlet fitting. Inspect hose condition and replace if cracked or deteriorated.
   ⚠Hoses may be brittle from heat exposure. Work carefully to avoid tearing.
4. 4

   Disconnect outlet pipe
   Disconnect the outlet pipe from the check valve to the exhaust manifold. This may be secured with a clamp or flange connection. If a flange connection, remove the mounting bolts. Apply penetrating oil if fasteners show corrosion.
   ℹ️Mark orientation of check valve before removal to ensure correct flow direction on installation.
   Torque spec

   Mounting Bolts31 Nm (23 lb-ft)
5. 5

   Remove check valve mounting hardware
   Remove the bolts or bracket securing the check valve to its mounting location. The check valve is typically mounted to a bracket near the engine block or on the exhaust manifold area. Support the check valve while removing the final fastener.
6. 6

   Remove check valve assembly
   Carefully remove the check valve from the engine bay. Note the orientation and flow direction arrow on the valve body. Inspect the mounting location for debris or damage.
7. 7

   Clean mating surfaces
   Use a wire brush to clean the inlet and outlet connection points. Remove any carbon deposits, old gasket material, or debris from the mounting surfaces. Use a shop vacuum to remove loose debris and prevent contamination of the air injection system.
8. 8

   Prepare new check valve
   Unpack the new check valve and verify correct part number and flow direction arrow. Install new gasket onto the outlet flange if applicable. Apply anti-seize compound to threaded mounting fasteners (not to gasket surfaces).
   ⚠Verify flow direction arrow points toward exhaust manifold. Incorrect installation will cause system failure.
9. 9

   Install check valve assembly
   Position the new check valve in the mounting location, ensuring correct orientation with flow arrow pointing toward the exhaust. Thread mounting bolts by hand initially to ensure proper alignment before tightening.
10. 10

    Secure check valve mounting
    Torque the check valve mounting bolts to specification in a cross-pattern if multiple bolts are present. Ensure the valve is secure and properly aligned with inlet and outlet connections.
    Torque spec

    Mounting Bolts31 Nm (23 lb-ft)
11. 11

    Connect outlet pipe
    Reconnect the outlet pipe to the check valve outlet fitting. If using a flanged connection, ensure gasket is properly seated and install flange bolts. Apply anti-seize to exhaust flange bolts and torque to specification.
    Torque spec

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

    Connect inlet air hose
    Slide the inlet air hose onto the check valve inlet fitting, ensuring it is fully seated. Position a new hose clamp (or reuse if in good condition) approximately 1/2 inch from the end of the hose and tighten securely.
13. 13

    Reinstall heat shields and covers
    Reinstall any heat shields or protective covers that were removed for access. Torque heat shield bolts to specification.
    Torque spec

    Heat Shield Bolts10 Nm (7 lb-ft)
14. 14

    Reinstall engine cover and reconnect battery
    Press the engine cover back onto its mounting grommets until fully seated. Reconnect the negative battery terminal and tighten securely.

Reassembly

1. Ensure all hose clamps are properly tightened and hoses are fully seated on fittings
2. Verify check valve flow direction arrow points toward exhaust manifold
3. Confirm all heat shields and covers are reinstalled to prevent heat damage to surrounding components
4. Double-check that no tools or parts were left in the engine bay

Verification

• Start engine and listen for unusual hissing or air leak sounds from the check valve area
• Allow engine to reach operating temperature and verify no exhaust leaks at the check valve outlet connection
• Monitor for check engine light or diagnostic trouble codes related to secondary air injection system (P0410, P0411, P0412)
• Perform a test drive and verify smooth operation with no unusual sounds from the engine bay
• If equipped with secondary air system monitor on scan tool, verify system passes functional test during cold start conditions

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