Air Injection Check Valve

This procedure covers the removal and replacement of the air injection check valve on the 5.0L Coyote V8 engine, which prevents exhaust backflow into the secondary air injection system.

Warnings

Tools required

Parts

• Air injection check valve × 1 — Use OEM specification
• Check valve gasket × 1 — Use OEM specification
• Exhaust flange gasket (if damaged) × 1 — Use OEM specification

Preparation

1. Ensure engine and exhaust system are completely cool to the touch
2. Park vehicle on level ground and apply parking brake
3. Disconnect negative battery terminal to prevent accidental air pump activation
4. Raise front of vehicle if additional clearance is needed for access (optional depending on approach)
5. Locate the air injection check valve on the passenger side of the engine near the exhaust manifold

Procedure

1. 1

   Remove engine cover
   Remove the plastic engine cover by pulling upward on the cover to disengage the retaining grommets. Set aside in a clean location.
2. 2

   Disconnect air injection supply line
   Locate the air supply hose connecting from the secondary air injection pump to the check valve. Loosen the hose clamp and disconnect the air supply hose from the inlet side of the check valve. Move the hose out of the work area.
3. 3

   Spray exhaust connections with penetrating oil
   Apply penetrating oil to the check valve mounting bolts and the exhaust flange connection. Allow to soak for 10-15 minutes to ease removal and reduce risk of breaking corroded fasteners.
4. 4

   Remove check valve mounting bolts
   Using the appropriate socket, remove the bolts securing the check valve to its mounting bracket or exhaust connection point. Support the check valve assembly while removing the final bolt. Note the orientation and position of any spacers or brackets for reinstallation.
   Torque spec

   Mounting Bolts34 Nm (25 lb-ft)
5. 5

   Disconnect exhaust pipe connection
   Remove the exhaust flange bolts connecting the check valve outlet to the exhaust pipe. Carefully separate the connection and remove the old gasket. Inspect the exhaust flange for damage or warping.
   Torque spec

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

   Remove check valve assembly
   Remove the check valve assembly from the vehicle. Inspect all mounting points and mating surfaces for damage, corrosion, or cracks that may affect sealing.
7. 7

   Clean mating surfaces
   Using a wire brush or scraper, thoroughly clean all gasket mating surfaces on the exhaust pipe flange and mounting bracket. Remove all old gasket material, carbon deposits, and corrosion. Ensure surfaces are flat and smooth for proper sealing.
8. 8

   Prepare new check valve
   Unpack the new check valve and verify it matches the original part. Install a new gasket onto the check valve. Verify the check valve arrow or flow direction marking points toward the exhaust system (away from the air pump).
   ⚠Installing the check valve backward will cause immediate system failure and may damage the air injection pump.
9. 9

   Install new check valve to exhaust pipe
   Position the new check valve with gasket to the exhaust pipe flange. Apply anti-seize compound to the exhaust flange bolt threads. Start all flange bolts by hand to ensure proper alignment, then torque in a crossing pattern to specification.
   Torque spec

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

    Secure check valve mounting bolts
    Align the check valve assembly to the mounting bracket, ensuring all spacers and hardware are properly positioned. Install mounting bolts and torque to specification. Verify the check valve is secure and properly oriented.
    Torque spec

    Mounting Bolts34 Nm (25 lb-ft)
11. 11

    Reconnect air supply line
    Reconnect the air injection supply hose to the inlet side of the check valve. Ensure the hose is fully seated and tighten the hose clamp securely. Check that the hose routing does not contact hot exhaust components.
12. 12

    Reinstall engine cover
    Reinstall the plastic engine cover by aligning the grommets with the mounting posts and pressing down firmly until all grommets are fully seated.
13. 13

    Reconnect battery and lower vehicle
    Reconnect the negative battery terminal. If vehicle was raised, carefully lower it to the ground and remove jack stands.

Reassembly

1. Ensure all exhaust connections are tight and gaskets are properly seated to prevent exhaust leaks
2. Verify air supply hose is securely connected and routed away from hot exhaust components
3. Double-check that the check valve flow direction arrow points toward the exhaust (away from pump)

Verification

• Start the engine and listen for any exhaust leaks at the check valve connections. A hissing sound indicates a leak that must be corrected
• Allow engine to reach operating temperature and verify no leaks develop when exhaust components expand
• During cold start, the secondary air injection pump should activate briefly (1-2 minutes). Listen for normal pump operation without abnormal rattling or backfire sounds
• Use a scan tool to check for any secondary air injection system diagnostic trouble codes. Clear any pre-existing codes and verify none return
• After test drive, recheck all connections for tightness and verify no exhaust odors are present in the engine compartment

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