321C CR Excavator Hydraulic System Caterpillar

Note: Adjustment procedures must be performed before a test and adjustment of any line relief valve pressure setting is attempted. A temporary setting of the main relief valve pressure is required before any line relief valve pressure setting is adjusted. Refer to the adjustment procedures in Testing And Adjusting, "Relief Valve (Main) - Test and Adjust".

Test

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	g00952442
Pump compartment (1) Pressure tap (delivery pressure of the drive pump ) (2) Pressure tap (delivery pressure of the idler pump ) (3) Pressure tap (power shift pressure)

4. Connect a 60000 kPa (8700 psi) pressure gauge to pressure tap (1) .

5. Connect a 60000 kPa (8700 psi) pressure gauge to pressure tap (2) .

6. Connect a 6000 kPa (870 psi) pressure gauge to pressure tap (3) . This is used to monitor power shift pressure.

7. Start the engine.

8. Place the machine controls at the following settings: engine speed dial 10 and AEC switch OFF. Refer to Testing and Adjusting, "Engine Performance - Test" for engine rpm settings.

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

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Illustration 2	g00672009
Monitor (A) Message display (B) Keypad (C) Up key (D) Left key (E) Down key (F) Right key (G) Cancel key (H) Set key (I) OK key (J) Menu key

10. Start Service Mode and input a fixed power shift pressure of 2900 kPa (420 psi).

    1. Press menu key (J) .

       Note: If more than thirty seconds pass between pushing the keys on the keypad, the menu mode will be cancelled and the previous display will be restored to message display (A) .

    2. Press down key (E) in order to highlight the menu item "SERVICE OPTIONS" on the message display. Press OK key (I) .

    3. Input the password "FFF2". Press left key (D) or right key (F) in order to change the position of the flashing character. Press up key (C) or press down key (E) in order to change the value of the flashing character. Press OK key (I) after the correct password is displayed.

    4. Press down key (E) once in order to highlight the second line on the message display.

    5. Press right key (F) repeatedly until "DEVICE TEST" appears on the message display.

    6. Press down key (E) in order to move down one line on the message display.

    7. Press right key (F) until the "PS PRV - FIXED" appears on the message display.

    8. Press down key (E) .

    9. Press OK key (I) . The display on line 4 of the message display will now change to a numeric value. These characters represent the power shift pressure (kPa).

    10. Press left key (D) or right key (F) in order to increase or decrease the numeric value that is displayed on line 4 of the message display. Pressing left key (D) one time decreases the power shift pressure 10 kPa (1.5 psi). Pressing right key (F) one time increases the power shift pressure 10 kPa (1.5 psi).

        Note: The value for power shift pressure on the monitor may not always match the pressure reading on the pressure gauge. Adjust the value on the monitor until the desired power shift pressure is attained on the pressure gauge that is connected to the pressure tap for power shift pressure. The actual power shift pressure must be 2900 kPa (420 psi) on the pressure gauge.

        Note: To prevent a change in power shift pressure during the relief valve adjustment, do not turn the engine start switch to the OFF position.

        Note: Refer to Service Manual, "Engine And Pump Electronic Control System" for additional information on Service Mode.

11. The pressure setting for both the head end and the rod end for each cylinder is 36800 ± 1470 kPa (5350 ± 215 psi).

Illustration 3	g00952447
Main control valves (front view) (7) Line relief valve (boom cylinder rod end) (8) Line relief valve (bucket cylinder head end) (9) Line relief valve (stick cylinder head end)

The following line relief valves are located on top of the main control valves: boom cylinder rod end, bucket cylinder head end and stick cylinder head end. The line relief valve for the bucket cylinder rod end is located under the main control valves and opposite the line relief valve for bucket cylinder head end (8) .

Illustration 4	g00671871
Main control valve (bottom view) (10) Boom drift reduction valve (11) Line relief valve (boom cylinder head end)

The line relief valve (boom cylinder head end) (11) is located on boom drift reduction valve (10) .

Illustration 5	g00671874
Main control valve (bottom view) (12) Line relief valve (stick cylinder rod end) (13) Stick drift reduction valve

The line relief valve (stick cylinder head end) (12) is located on stick drift reduction valve (13) .

Illustration 6	g00343372
Line relief valve (typical example) (14) Locknut (15) Adjustment screw

Note: After relief valve adjustments, cancel Service Mode.

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 (2) .

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

4. Loosen locknut (14) on the stick line relief valve. Turn adjustment screw (15) until the pressure gauge reading at pressure tap (2) is 36800 ± 1470 kPa (5350 ± 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 (2) .

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

8. Loosen locknut (14) on the stick line relief valve. Turn adjustment screw (15) until the pressure gauge reading at pressure tap (2) is 36800 ± 1470 kPa (5350 ± 215 psi).

9. After completion of line relief valve adjustment, tighten locknut (14) .

Note: Turning adjustment screw (15) clockwise increases the pressure. Turning adjustment screw (15) 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 (1) .

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

4. Loosen locknut (14) on the bucket line relief valve. Turn adjustment screw (15) until the pressure gauge reading at pressure tap (1) is 36800 ± 1470 kPa (5350 ± 215 psi).

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

6. Check the pressure in the bucket cylinder rod end on the pressure gauge at pressure tap (1) .

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

8. Loosen locknut (14) on the bucket line relief valve. Turn adjustment screw (15) until the pressure gauge reading at pressure tap (1) is 36800 ± 1470 kPa (5350 ± 215 psi).

9. After completion of line relief valve adjustment, tighten locknut (14) .

Note: Turning adjustment screw (15) clockwise increases the pressure. Turning adjustment screw (15) 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 (1) .

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

4. Loosen locknut (14) on the boom line relief valve. Turn adjustment screw (15) until the pressure gauge reading at pressure tap (1) is 36800 ± 1470 kPa (5350 ± 215 psi).

Note: In order to adjust the line relief valve pressure setting for the boom cylinder rod end, a temporary adjustment of the line relief valve for the bucket cylinder rod end must be performed.

5. Loosen locknut (14) on the line relief valve for the BUCKET OPEN function. Turn adjustment screw (15) by one half turn in a clockwise direction. Tighten locknut (14) on the line relief valve for the bucket cylinder.

6. Move the joystick for the bucket until the bucket is at the full BUCKET OPEN position (full retraction of the bucket cylinder). Hold the joystick for the bucket in this position. At the same time, move the joystick for the boom until the boom is at the full BOOM DOWN position (full retraction of boom cylinders). Hold the joystick for the boom in this position.

7. Check the pressure in the boom cylinder rod end on the pressure gauge at pressure tap (1) .

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

9. Loosen locknut (14) on the boom line relief valve. Turn adjustment screw (15) until the pressure gauge reading at pressure tap (1) is 36800 ± 1470 kPa (5350 ± 215 psi).

10. Tighten locknut (14) on the boom line relief valve.

    Note: Turning adjustment screw (15) clockwise increases the pressure. Turning adjustment screw (15) counterclockwise decreases the pressure.

    Note: Always make final pressure adjustment on pressure rise.

11. After completion of line relief valve adjustment for the boom cylinders, return the line relief valve pressure setting of the bucket to the specified pressure setting.

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.