311B and 312B Excavators Hydraulic System Caterpillar

Test

1. Place the machine on level ground.

2. Stop the engine.

3. Release the pressure in the hydraulic system. Refer to Testing and Adjusting, "Hydraulic System Pressure - Release".
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   Illustration 1	g00379594
   Pump compartment (1) Pressure tap (power shift pressure) (2) Pressure tap (rear pump delivery pressure) (3) Pressure tap (front pump delivery pressure)

4. Connect a 60000 kPa (8700 psi) pressure gauge to either pressure tap (2) or pressure tap (3).
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   Illustration 2	g00380113
   Pilot oil manifold compartment (25) Pilot relief valve (26) Pressure tap (27) Adjustment screw (28) Locknut

5. Connect a 6000 kPa (870 psi) pressure gauge to pressure tap (26).

6. Start the engine.

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

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

   Reference: Make reference to Testing and Adjusting, "Operational Checks" for engine rpm settings.

9. Check the pilot relief valve setting at pressure tap (26).

Adjust

1. Loosen locknut (28).

2. Turn adjustment screw (27) until the pressure gauge reading at pressure tap (26) is 4100 ± 200 kPa (595 ± 29 psi).

3. Tighten locknut (28) to a torque of 16 ± 1 N·m (12 ± 1 lb ft).

Note: Turning adjustment screw (27) clockwise increases the pressure. Turning adjustment screw (27) counterclockwise decreases the pressure.

Note: Always make final pressure adjustments on pressure rise.

Note: Normal operation of the engine and pumps are necessary for the pressure adjustment. If the results of the pressure adjustments are not correct, then the engine and the pump characteristic curve needs to be checked.