Cowl-Mounted Air Cleaner

4700 mm 09.02.003

The standard cowl-mounted air cleaner system used on Western Star trucks is a reverse air flow design. The air flow in this system flows from the inside of the element, outward through the filter element into the canister, then into the air intake piping on route to the turbocharger. It is highly recommended that only original equipment filter elements are used to service the air cleaner assemblies. Aftermarket replacement elements may vary in size to the original equipment, or may use a different type of seal at the top and bottom of the element. A variance in the size of the element, or the thickness and type of seal material, can affect the crush of the gasket seal and could result in a poor seal on one of the mating surfaces. Elements that do not fit properly may allow the element to bounce in the canister and allow dirt to pass over the upper seal and into the canister and intake piping.

If the vehicle is equipped with dual air cleaners, replace both elements at the same interval.

  1. Remove the cap nuts that secure the service cover to the canister. See Fig.. Take note of the orientation of the air intake screen so the service cover can be reinstalled in the correct position.

    1. Cap Nut

    2. Service Cover

    3. Service Cover Gasket

    4. Filter Element

    5. Mounting Band

    6. Canister

    Fig. 1, Cowl-Mounted Air Cleaner

  2. After removing the canister cap, carefully pull the element straight up out of the canister, ensuring no dust or debris is dropped into the canister.
  3. Inspect the clean side of the element and canister for evidence of contamination. The clean side of the element is the area outside the gaskets on either end of the element, including the top cover. If debris is present, find the leak, determine the cause, and correct the problem area immediately.
  4. Clean the inside of the canister thoroughly. Use a clean damp cloth to wipe every surface clean. If unable to remove all debris, use a vacuum cleaner to remove all remaining dirt, dust, and contamination.
  5. Clean the gasket sealing surfaces of the canister. Properly fitted gaskets are crucial to prevent dirt from entering the canister. Use a damp cloth to wipe clean and remove any hard ridges of dirt built up around the old gasket sealing area on the top cover and the bottom of the canister.
  6. Apply pressure to the new gasket with your fingers to test for resilience. When you release pressure, the gasket should instantly spring back to its original shape.

    7. Note: The element will be sitting higher than normal until the cover bolts compress the gaskets.

  7. Slide in the new element, ensuring that the bottom gasket seats firmly. Install a new cover gasket, making sure the sealing area around the studs is clean and free of any old gasket material.
  8. Inspect the threaded area of the studs. They should be clean and free of corrosion and foreign material. Apply a light coating of oil. Inspect the cap nuts. If wear is apparent replace them with new ones. Torque the cap nuts in sequence 96 lbf·in (1080 N·cm). Do not over-tighten the cap nuts. Be certain that the cover has pulled down evenly around the canister, because both element gaskets and the cover gasket are being compressed as the cap nuts are tightened.
  9. Recheck the torque of the canister band mounting clamps and be certain the blank portion of the top cap screen area is facing forward.
  10. Press the reset button on the bottom of the air restriction indicator to reset to zero. If the indicator fails to reset to zero, replace it with a new one. If the truck is not equipped with a restriction indicator or a dash-mounted restriction gauge, check that the pipe plugs located in the canister, or in the aluminum piping just before the turbocharger, are tight and correctly torqued.
Note:
Parent topic: Air Cleaner Element Inspection and Replacement
Document Number: 0000120158
Manual Publication Date: 2024-05-23
Topic Publication Date: 2024-10-31