Air Injection Check Valve

Replace the air injection check valve on the 6.7L Cummins diesel emissions system to restore proper secondary air flow and prevent exhaust backflow into the air injection pump.

Warnings

Tools required

Parts

• Air injection check valve × 1 — Use OEM specification
• Air injection pipe gaskets/seals × 1 — Use OEM specification

Preparation

1. Ensure engine is completely cool to the touch
2. Park vehicle on level surface and engage parking brake
3. Disconnect negative battery cable to prevent accidental starting
4. Spray all exhaust fasteners with penetrating oil and allow 15-30 minutes soak time
5. Raise and support vehicle on jack stands if improved access is needed

Procedure

1. 1

   Access the air injection system
   Locate the air injection check valve on the passenger side of the engine bay. Remove any heat shields or protective covers that obstruct access to the check valve assembly. The check valve is typically positioned between the air injection pump and the exhaust manifold connection.
2. 2

   Disconnect air injection supply line
   Disconnect the air supply line from the air injection pump side of the check valve. Note the orientation of any clamps or fittings. Inspect the supply line for cracks or damage and replace if necessary.
3. 3

   Remove exhaust side connection
   Disconnect the check valve from the exhaust manifold or downpipe connection. Remove the exhaust flange bolts carefully, working gradually to avoid breaking studs. If the connection is seized, apply additional penetrating oil and allow more soak time. Keep track of any gaskets or sealing rings.
4. 4

   Remove check valve mounting
   Remove the mounting bolts that secure the check valve bracket to the engine or frame. Support the check valve assembly as you remove the final fasteners to prevent it from falling.
5. 5

   Remove old check valve
   Extract the check valve assembly from the vehicle. Inspect the mounting location and connections for excessive carbon buildup, cracks, or damage. Take note of the valve orientation and any alignment marks.
6. 6

   Clean mounting surfaces
   Use a wire brush to thoroughly clean all mounting surfaces, exhaust flange surfaces, and connection points. Remove all carbon deposits, old gasket material, and corrosion. Ensure surfaces are flat and smooth for proper sealing.
7. 7

   Prepare new check valve
   Unpack the new check valve and verify it matches the original. Apply anti-seize compound to the exhaust flange bolt threads. Install new gaskets or seals on the check valve connections according to manufacturer specifications.
8. 8

   Install new check valve
   Position the new check valve in the mounting location, ensuring proper orientation with the arrow on the valve body pointing toward the exhaust system (flow direction). Align all mounting points and start all fasteners by hand before tightening any.
9. 9

   Secure mounting bolts
   Tighten the check valve mounting bolts to specification using a torque wrench. Follow a cross-pattern sequence if multiple bolts are present to ensure even clamping pressure.
10. 10

    Connect exhaust side
    Install the exhaust connection with a new gasket. Apply anti-seize compound to the exhaust flange bolt threads as specified. Tighten the exhaust flange bolts in a cross-pattern to the specified torque to ensure even sealing and prevent leaks.
11. 11

    Reconnect air supply line
    Reconnect the air injection supply line to the inlet side of the check valve. Ensure all clamps and fittings are properly seated and tightened securely. Verify there are no kinks or restrictions in the supply line.
12. 12

    Reinstall heat shields and covers
    Reinstall any heat shields or protective covers removed during disassembly. Torque all cover and heat shield fasteners to specification.
13. 13

    Final checks and reconnection
    Verify all connections are secure and all tools have been removed from the engine bay. Reconnect the negative battery cable. Double-check that no fasteners were left loose and no components are interfering with moving parts.

Reassembly

1. Ensure all exhaust connections are properly torqued to prevent exhaust leaks
2. Verify proper orientation of check valve with flow arrow pointing toward exhaust
3. Confirm all heat shields are reinstalled to prevent heat damage to surrounding components

Verification

• Start the engine and listen for exhaust leaks at the check valve connections. Address any leaks immediately.
• Allow engine to reach operating temperature and verify no abnormal noises from the air injection system
• Check for diagnostic trouble codes related to the air injection system using a scan tool
• Verify proper operation of the air injection system during cold start when the system is most active
• Inspect all connections after the first heat cycle for any signs of leakage or loosening

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

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