330B Excavator Hydraulic System Caterpillar

Test

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

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

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Illustration 1	g00363032
Pump compartment (1) Pressure tap (power shift pressure) (2) Pressure tap (upper pump delivery pressure) (3) Pressure tap (lower pump delivery pressure)

3. Attach a 60000 kPa (8700 psi) pressure gauge to pressure tap (3) .

4. Start the engine.

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

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

7. Open the bucket until the bucket cylinder rod is at the full retraction.

8. Check the main relief valve pressure setting at pressure tap (3) .

Adjust

Illustration 2	g00341013
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 34300 ± 490 kPa (4950 ± 72 psi).

2. To adjust the main relief valve pressure, loosen locknut (5) and turn adjustment screw (4) until the pressure gauge reading at pressure tap (3) is 34300 ± 490 kPa (4950 ± 72 psi).

3. 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.