307C Excavator Hydraulic System Caterpillar

Note: A temporary setting of the main relief valve pressure is required before any line relief valve pressure setting is adjusted. The main relief valve pressure setting should be 27500 ± 490 kPa (4000 ± 72 psi). If the main relief valve is not within the specification, adjust the main relief valve pressure setting to the correct pressure specification. Refer to Testing and Adjusting, "Relief Valve (Main) - Test and Adjust".

Preparation

1. Position 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	g00727889
Pump compartment (1) Pressure tap (right pump delivery pressure) (2) Pressure tap (left pump delivery pressure)

4. Connect a 60000 kPa (8700 psi) pressure gauge to pressure tap (1). This is used to monitor the line relief valve pressure setting of the stick cylinder.

5. Connect a 60000 kPa (8700 psi) pressure gauge to pressure tap (2). This is used to monitor the line relief valve pressure setting of the boom cylinders and the bucket cylinder.

Illustration 2	g00730727
Main control valves (front view) (9) Line relief valve (stick cylinder head end) (10) Line relief valve (boom cylinder rod end) (11) Line relief valve (bucket cylinder head end)

The following line relief valves are located on top of the main control valves: stick cylinder head end (9), boom cylinder rod end (10) and bucket cylinder head end (11). The line relief valve for the stick cylinder rod end and the line relief valve for the boom cylinder head end are located under the main control valve.

Illustration 3	g00395463
Line relief valve (typical example) (12) Locknut (13) Adjustment screw

Note: Return the main relief valve pressure to the specified setting after testing and adjusting any line relief valve. Refer to Testing And Adjusting, "Relief Valve (Main) - Test and Adjust" for the main relief valve pressure setting.

Adjustment (Stick Cylinder)

1. To adjust the line relief valve pressure setting of the stick cylinder rod end, move the joystick for the stick until the stick is at the full STICK OUT position (full retraction of stick cylinder). Hold the joystick for the stick in this position.

2. Check the pressure in the stick cylinder rod end on the pressure gauge at pressure tap (1) .

3. Return the joystick for the stick to the NEUTRAL position.

4. Loosen locknut (12) on the stick line relief valve. Turn adjustment screw (13) until the pressure gauge reading at pressure tap (1) is 30900 ± 1470 kPa (4500 ± 215 psi).

5. To adjust the line relief valve pressure setting of the stick cylinder head end, move the joystick for the stick until the stick is at the full STICK IN position (full extension of stick cylinder). Hold the joystick for the stick in this position.

6. Check the pressure in the stick cylinder head end on the pressure gauge at pressure tap (1) .

7. Return the joystick for the stick to the NEUTRAL position.

8. Loosen locknut (12) on the stick line relief valve. Turn adjustment screw (13) until the pressure gauge reading at pressure tap (1) is 30900 ± 1470 kPa (4500 ± 215 psi).

9. After completion of line relief valve adjustment, tighten locknut (12) to a torque of 29 ± 2 N·m (21 ± 1 lb ft).

Note: Turning adjustment screw (13) clockwise increases the pressure. Turning adjustment screw (13) counterclockwise decreases the pressure.

Note: Always make final pressure adjustment on pressure rise.

Adjustment (Bucket Cylinder)

1. To adjust the line relief valve pressure setting of the bucket cylinder head end, move the joystick for the bucket until the bucket is at the full BUCKET CLOSE position (full extension of bucket cylinder). Hold the joystick for the bucket in this position.

2. Check the pressure in the bucket cylinder head end on the pressure gauge at pressure tap (2) .

3. Return the joystick for the bucket to the NEUTRAL position.

4. Loosen locknut (12) on the bucket line relief valve. Turn adjustment screw (13) until the pressure gauge reading at pressure tap (2) is 30900 ± 1470 kPa (4500 ± 215 psi).

5. After completion of line relief valve adjustment, tighten locknut (12) to a torque of 29 ± 2 N·m (21 ± 1 lb ft).

Note: Turning adjustment screw (13) clockwise increases the pressure. Turning adjustment screw (13) counterclockwise decreases the pressure.

Note: Always make final pressure adjustment on pressure rise.

Adjustment (Boom Cylinders)

1. To adjust the line relief valve pressure setting of the boom cylinder head end, move the joystick for the boom until the boom is at the full BOOM RAISE position (full extension of boom cylinders). Hold the joystick for the boom in this position.

2. Check the pressure in the boom cylinder head end on the pressure gauge at pressure tap (2) .

3. Return the joystick for the boom to the NEUTRAL position.

4. Loosen locknut (12) on the boom line relief valve. Turn adjustment screw (13) until the pressure gauge reading at pressure tap (2) is 30900 ± 1470 kPa (4500 ± 215 psi).

Note: Use engine low idle speed in order to adjust the line relief valve pressure setting of the boom cylinder rod end. Refer to Testing and Adjusting, "Engine Performance - Test" for engine rpm settings.

5. To adjust the line relief valve pressure setting of the boom cylinder rod end, move the joystick for the boom until the boom is at the full BOOM LOWER position (full retraction of boom cylinders). Hold the joystick for the boom in this position.

6. Check the pressure in the boom cylinder rod end on the pressure gauge at pressure tap (2) .

7. Return the joystick for the boom to the NEUTRAL position.

8. Loosen locknut (12) on the boom line relief valve. Turn adjustment screw (13) until the pressure gauge reading at pressure tap (2) is 30900 ± 1470 kPa (4500 ± 215 psi).

9. After completion of line relief valve adjustment, tighten locknut (12) to a torque of 29 ± 2 N·m (21 ± 1 lb ft).

   Note: Turning adjustment screw (13) clockwise increases the pressure. Turning adjustment screw (13) counterclockwise decreases the pressure.

   Note: Always make final pressure adjustment on pressure rise.

Note: If an appropriate location is not available to fully extend the boom cylinders, exchange the functions of the boom line relief valves. Remove the line relief valve for the boom cylinder head end and the line relief valve for the boom cylinder rod end from the main control valve. Exchange the location in the main relief valve of the line relief valves. Adjust the pressure of the boom line relief valve that is now attached in the head end. After completion of line relief valve adjustment, return the respective line relief valves to the original locations.