302.5C Mini Hydraulic Excavator Hydraulic System Caterpillar

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	g01187753
View from back of the machine (1) Pilot manifold (2) Pilot relief valve (3) Pressure tap (pilot pump) (4) Main pump

4. Open the access door for the pump compartment.

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Illustration 2	g01187807
Pilot manifold (2) Pilot relief valve

5. Connect a 6000 kPa (870 psi) pressure gauge to pilot pressure tap (3) .

6. Start the engine.

7. Place the engine speed lever at the HIGH IDLE position. Refer to Testing and Adjusting, "Engine Performance - Test (Engine Speed)" for engine rpm settings.

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

9. Check the pilot relief valve setting at pilot pressure tap (3) .

10. The pilot relief valve setting should be 3400 ± 200 kPa (495 ± 30 psi). If the pilot relief valve setting is not within the specification, adjust the pilot relief valve.

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.

Adjustment of the Pilot Relief Valve

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Illustration 3	g01186674
Pilot relief valve (5) End cap (6) Adjustment screw (7) Spring

1. Remove end cap (5) from pilot relief valve (2) .

2. Turn adjustment screw (6) in order to adjust the pilot relief valve. Turn adjustment screw (6) clockwise in order to increase pressure. Turn adjustment screw (6) counterclockwise in order to decrease the pressure.

3. Install end cap (5) . Use Step 5 through Step 10 in order to check the pressure of the pilot system.

Note: Always make final adjustment 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.