W345B Series II Excavator Hydraulic System Relief Valve (Main) - Test and Adjust Caterpillar


Relief Valve (Main) - Test and Adjust
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1.1. Temporary Setting of the Main Relief Valve

  1. Position the machine on level ground and stop the engine.

  1. Release the pressure in the hydraulic system. Refer to Testing and Adjusting, "Hydraulic System Pressure - Release".



    Illustration 1g00694582

    Pump compartment

    (1) Pressure tap (power shift pressure)

    (2) Pressure tap (upper pump delivery pressure)

    (3) Pressure tap (lower pump delivery pressure)

  1. Attach a 60000 kPa (8700 psi) pressure gauge to pressure tap (2) .

  1. Start the engine.

  1. Place the machine controls at the following settings: Power Mode and engine speed dial "10".

    Note: The engine will not reach maximum no-load speed until the hydraulic tank pressure has reached the operating level.

  1. Increase the hydraulic oil temperature to 55° ± 5°C (131° ± 9°F).

  1. Open the grapple until the grapple cylinder rod is at the full retraction.

  1. Check the main relief valve pressure setting at pressure tap (2) .



    Illustration 2g00299702

    Main control valve (top view)

    (4) Adjustment screw

    (5) Locknut

    (6) Main relief valve

  1. Return the control lever to the NEUTRAL position. Adjust the main relief valve pressure.

  1. To adjust the main relief valve pressure, loosen locknut (5) and turn adjustment screw (4) until the pressure gauge reading at pressure tap (2) is 35170 to 35860 kPa (5100 to 5200 psi).

  1. Tighten locknut (5) to a torque of 50 ± 10 N·m (37 ± 7 lb ft).

Note: Turning adjustment screw (4) clockwise increases the pressure. Turning adjustment screw (4) counterclockwise decreases the pressure.

Note: Always make final pressure adjustments on pressure rise.

Temporary Setting of the Main Relief Valve

Note: The main relief valve must be adjusted to a temporary pressure setting before any line relief valve can be adjusted.




    Illustration 3g00694582

    Pump compartment

    (1) Pressure tap (power shift pressure)

    (2) Pressure tap (upper pump delivery pressure)

    (3) Pressure tap (lower pump delivery pressure)

  1. Position the machine on level ground.

  1. Stop the engine.

  1. Release the pressure in the hydraulic system. Refer to Testing and Adjusting, "Hydraulic System Pressure - Release".

  1. Connect a 60000 kPa (8700 psi) pressure gauge to pressure tap (2).

  1. Start the engine.

  1. Increase the hydraulic oil temperature to 55° ± 5°C (131° ± 9°F).

  1. Place the machine controls at the following settings: Power Mode, engine speed dial "10" and AEC switch OFF.

    Note: The engine will not reach maximum no-load speed until the hydraulic tank pressure has reached the operating level.

    Reference: Refer to Testing and Adjusting, "Engine Performance - Test" for engine rpm settings.

  1. Open the grapple until the grapple cylinder rod is at the full retraction.

  1. Check the main relief valve pressure setting at pressure tap (2) .



    Illustration 4g00299702

    Main control valve (top view)

    (4) Adjustment screw

    (5) Locknut

    (6) Main relief valve

  1. Be sure that the main relief valve pressure is set at 35170 to 35860 kPa (5100 to 5200 psi).

    Note: Always make final pressure adjustments on pressure rise.

  1. Loosen locknut (5). Turn adjustment screw (4) clockwise by two-thirds of a turn. Tighten locknut (5) .

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