325D and 329D Excavators Hydraulic System Oil Filter (Return) - Replace Caterpillar


Hydraulic System Oil Filter (Return) - Replace
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------ WARNING! ------

Hot oil and hot components can cause personal injury. Do not allow hot oil or hot components to contact skin.


The return filter is a cartridge type filter. The amount of foreign material that enters the hydraulic system is reduced when the filter element is replaced.

Two different filters are available for the return filter. One filter is used for standard applications such as digging and normal use of a hammer. The second filter is used for an application such as demolishing a ceiling in a tunnel with a hammer.

Note: If the message display shows that the hydraulic return filter is plugged, turn off the machine. After you make sure that the warning has disappeared, start the machine and run the machine on level ground for approximately 10 minutes. If the warning still appears in the message display, inspect the filter and replace the filter, if necessary.



    Illustration 1g01220269

  1. Loosen the fill/vent plug in order to relieve the hydraulic tank pressure. Tighten the fill/vent plug after the hydraulic tank pressure is relieved.

    Note: The return filter cartridge is located on the side of the hydraulic tank.

  2. Remove the filter cartridge. Perform Step 2a through Step 2f in order to remove the filter cartridge.


      Illustration 2g00102211
      (1) Bolts
      (2) Washers
      (3) Cover
      (4) Plug
      (5) Filter cartridge

    1. Remove bolts (1), washers (2), and cover (3).

      Note: Refer to Operation and Maintenance Manual, "General Hazard Information" for information on containing fluid spillage.

    2. Remove plug (4) in order to release the pressure in filter cartridge (5).

      Note: When plug (4) is removed the oil level in the return filter drops to the level of the hydraulic tank.



      Illustration 3g00102212
      (5) Filter cartridge
      (6) Filter case
      (A) Guide

    3. Pull up the handle at the top of filter cartridge (5) until the filter cartridge contacts guide (A) on filter case (6).


      Illustration 4g00102214

    4. Turn the filter cartridge counterclockwise by 180 degrees in order to align the projection of the filter cartridge with the notch of the filter case. Pull out the filter cartridge.


      Illustration 5g00102219
      (7) O-ring

    5. Inspect the cover and O-ring (7). If either part is damaged, replace the part.

    6. Inspect the filter cartridge for debris and for damage. If necessary, replace the filter cartridge.

  3. Remove the filter element. Perform Step 3a through Step 3f in order to remove the filter element.


      Illustration 6g00104507
      (4) Plug
      (8) Plate
      (18) O-ring

    1. Make sure that plug (4) is removed. Make sure that all of O-ring (18) is removed from plate (8).


      Illustration 7g00918893
      (8) Plate
      (9) Spiral retaining ring

    2. Remove spiral retaining ring (9).


      Illustration 8g00104510
      (8) Plate
      (10) Shell
      (11) O-ring
      (12) Filter element

    3. Hold the filter cartridge with one hand. Grasp the grip of plate (8) with your other hand. Lift plate (8) in order to separate plate (8) from the filter cartridge.

    4. Remove O-ring (11) from plate (8).

    5. Lift filter element (12) from shell (10).

    6. Pour the remaining oil into a suitable container.

      Note: Dispose of used oil according to local regulations.

    7. Repeat Step 3a through Step 3f for the other filter groups.

  4. Clean the shell of the filter cartridge. Perform Step 4a through Step 4d in order to clean the shell of the filter cartridge.


      Illustration 9g00104511
      (13) Slide plate
      (14) Pads
      (15) Screws
      (19) Port

    1. Turn shell (10) upside-down.

    2. Remove screws (15).

    3. Remove Pads (14) from slide plate (13).

    4. Wash the following parts in a clean nonflammable solvent: plug (4), plate (8), spiral retaining ring (9), shell (10) and Pads (14). Dry the parts.

  5. Install the filter elements. Perform Step 5a through Step 5k in order to install the filter elements.

    Note: Consult a AVSpare dealer for the Service Kit that is needed to install the filter element and the filter cartridge.

    1. Apply spray type oil to the inside of shell (10) in order to prevent rust.

    2. Apply grease to a new O-ring (11).

    3. Plate (8) will contact the inside of shell (10). Apply grease to this point.

    4. Apply grease to O-rings inside ports (19) at the bottom of shell (10).

    5. Install new Pads (14). Tighten the screws to a torque of 0.4 N·m (3.5 lb in).

    6. Apply spray type oil into the clearance between shell (10) and slide plate (13).


      Illustration 10g00104512
      (8) Plate
      (10) Shell
      (16) Boss
      (17) Notch

    7. Turn over shell (10). Apply grease to the two O-rings on new element (12). Install element (12) into shell (10).

    8. Move boss (16) in alignment with notch (17). Install plate (8) into shell (10).

    9. Install spiral retaining ring (9) into the groove in shell (10).

    10. Apply grease to new O-ring (18). Install O-ring (18) on plug (4).

    11. Install plug (4) into plate (8).

  6. Install the filter cartridge. Perform Step 6a through Step 6e in order to install the filter cartridge.


      Illustration 11g00102220
      (B) Port
      (C) Slide plate

    1. Check that ports (B) at the bottom of the filter case are closed.

      Note: If the ports are open, rotate slide plate (C) counterclockwise to the stopper in order to fully close the ports. When the ports are fully closed, any remaining oil in the filter case should be completely removed.



      Illustration 12g00102221
      (E) Slide plate
      (D) Port

    2. Check that ports (D) of the filter cartridge are fully closed.

      Note: The filter cartridge cannot be installed unless the ports are fully closed. If the ports are open, rotate slide plate (E) counterclockwise to the stopper in order to fully close the ports.



      Illustration 13g00102222
      (F) O-rings

    3. Check that O-rings (F) have been installed and that oil has been applied to O-rings (F).


      Illustration 14g00102225
      (1) Bolts

    4. Install the filter cartridge into the filter case. Turn the filter cartridge clockwise by 180 degrees and push down the filter cartridge when the filter cartridge contacts guide (A).

    5. Install plug (4), cover (3), washers (2), and bolts (1). Tighten bolts (1) to a torque of 29 ± 5 N·m (22 ± 4 lb ft).

  7. Check the hydraulic system oil level.

    Reference: For the correct procedure, refer to Operation and Maintenance Manual, "Hydraulic System Oil Level - Check".