330D, 336D and 340D Excavators Hydraulic System – Relief Valve (Main) – Test and Adjust

  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 1 g01266656

    Pump compartment

    (1) Pressure tap (delivery pressure for drive pump)

    (2) Pressure tap (delivery pressure for idler pump)

    (3) Pressure tap (power shift pressure)

  1. Attach a 60000 kPa (8700 psi) pressure gauge to pressure tap (1) and pressure tap (2) .
  1. Start the engine.
  1. Place the machine controls at the following settings: engine speed dial “10” and AEC switch OFF. Refer to Testing and Adjusting, “Engine Performance – Test (Engine Speed)” for engine rpm settings.
  1. Increase the hydraulic oil temperature to 55° ± 5°C (131° ± 9°F).
  1. Open the bucket until the bucket cylinder rod is at the full retraction.
  1. Check the main relief valve pressure setting at pressure tap (1) or pressure tap (2) .

    Illustration 2 g01241266

    Top of main control valve

    (4) Adjustment screw

    (5) Locknut

    (6) Main relief valve

  1. Return the control lever to the NEUTRAL position. Adjust the main relief valve pressure to 35000 + 500 – 1000 kPa (5076 + 73 – 145 psi).
  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 35000 + 500 – 1000 kPa (5076 + 73 – 145 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: A temporary setting of the main relief valve is required before any line relief valve can be adjusted.

    Illustration 3 g01266656

    Pump compartment

    (1) Pressure tap (delivery pressure for drive pump)

    (2) Pressure tap (delivery pressure for idler pump)

    (3) Pressure tap (power shift 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 (1) and 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: engine speed dial “10” and AEC switch OFF. Refer to Testing and Adjusting, “Engine Performance – Test (Engine Speed)” for engine rpm settings.
  1. Open the bucket until the bucket cylinder rod is at the full retraction.
  1. Check the main relief valve pressure setting at pressure tap (1) or pressure tap (2) .

    Illustration 4 g01241266

    Top of main control valve

    (4) Adjustment screw

    (5) Locknut

    (6) Main relief valve

  1. Be sure that the main relief valve pressure is set at 35000 + 500 – 1000 kPa (5076 + 73 – 145 psi).

    Note: Always make final pressure adjustments on pressure rise.

  1. Loosen locknut (5). Turn adjustment screw (4) clockwise for one half turn. Tighten locknut (5) .