321C CR Excavator Hydraulic System Caterpillar

Note: A temporary setting of the main relief valve is required before travel crossover relief valves can be tested. Refer to Testing And Adjusting, "Relief Valve (Main) - Test and Adjust".

1. Position the machine on level ground.

2. Stop the engine.

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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)

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

4. Connect a 60000 kPa (8700 psi) pressure gauge to pressure tap (1) . Use this pressure gauge to monitor the crossover relief valve pressure setting of the right travel motor.

5. Connect a 60000 kPa (8700 psi) pressure gauge to pressure tap (2) . Use this pressure gauge to monitor the crossover relief valve pressure setting of the left travel motor.

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Illustration 2	g00714259
Sprocket (left track) (16) Sprocket (17) FT-2547 Track block assembly

6. Place track block assembly (17) in sprocket (16) in order to block forward left travel. Refer to Illustration 2.

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 3	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.

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Illustration 4	g00671821
Travel brake valve (left side) (18) Locknut (19) Adjustment screw (20) Crossover relief valve (forward left travel) (21) Crossover relief valve (reverse left travel) (22) Locknut (23) Adjustment screw

11. Slowly move the left travel control lever to full FORWARD position and check the pressure gauge reading at pressure tap (2) . The pressure setting of crossover relief valve (20) should be 36800 ± 1470 kPa (5350 ± 215 psi).

12. Return the left travel control lever to the NEUTRAL position.

13. In order to adjust crossover relief valve (20) , loosen locknut (18) and turn adjustment screw (19) until the pressure gauge reading at pressure tap (2) is 36800 ± 1470 kPa (5350 ± 215 psi).

    Note: Turning adjustment screw (19) clockwise increases the pressure. Turning adjustment screw (19) counterclockwise decreases the pressure.

    Note: Always make final pressure adjustment on pressure rise.

14. Tighten locknut (18) to a torque of 130 ± 13 N·m (95 ± 10 lb ft).

    Note: Always make final pressure adjustments on pressure rise.

15. Place track block assembly (17) in sprocket (16) in order to block reverse left travel.

16. Slowly move the left travel lever to full REVERSE position and check the pressure gauge reading at pressure tap (2) . The pressure setting of crossover relief valve (21) should be 36800 ± 1470 kPa (5350 ± 215 psi).

17. Return the left travel control lever to the NEUTRAL position.

18. In order to adjust crossover relief valve (21) , loosen locknut (22) and turn adjustment screw (23) until the pressure gauge reading at pressure tap (2) is 36800 ± 1470 kPa (5350 ± 215 psi).

    Note: Turning adjustment screw (23) clockwise increases the pressure. Turning adjustment screw (23) counterclockwise decreases the pressure.

    Note: Always make final pressure adjustment on pressure rise.

19. Tighten locknut (22) to a torque of 130 ± 13 N·m (95 ± 10 lb ft).

    Note: Always make final pressure adjustments on pressure rise.

20. After relief valve adjustments, cancel Service Mode.

21. Return the main relief valve pressure to the specified setting after crossover relief valve pressure setting is attained.

In order to adjust the crossover relief valves on the right travel motor, place stopper (17) in the sprocket for right travel. Use the pressure gauge at pressure tap (1) in order to monitor the crossover relief valve pressure settings for the right travel motor. Adjust the crossover relief valves on the right travel motor in the same manner as the adjustment for the left travel motor.