320 GX and 323 GX Excavator Systems Relief Valve (Crossover) - Test and Adjust Caterpillar

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Personal injury or death can result from sudden machine movement. Sudden movement of the machine can cause injury to persons on or near the machine. To prevent injury or death, make sure that the area around the machine is clear of personnel and obstructions before operating the machine.

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Hot hydraulic oil under high pressure can remain in the components of the hydraulic system or the power train system after the engine has been stopped. The uncontrolled release of the hydraulic oil can cause sudden machine movement and can also result in the following conditions: Burns The penetration of body tissue Other personal injury Death If hydraulic oil penetrates body tissue, the injury must be treated immediately by a doctor who is familiar with this type of injury. Use a board or a piece of cardboard to check for a hydraulic oil leak. Make sure that all of the attachments have been lowered to the ground and that all trapped pressure has been released from the hydraulic system and the power train system. Also, make sure that the hydraulic oil is cool before the removal of any components or lines. Remove the hydraulic oil filler cap only when the engine is stopped and the filler cap is cool enough to touch with your bare hand.

Specification

References

Reference: Refer to the Operation and Maintenance Manual , "System Pressure Release" for the detailed procedure to release the system pressure.

Reference: Refer to the Operation and Maintenance Manual , "Prepare the Machine for Maintenance".

Reference: Refer to Testing and Adjusting, "Engine Performance - Test (Engine Speed)" for engine rpm settings.

Introduction

The crossover relief valves are located on the travel counterbalance valves. The following procedure will determine if the crossover relief valves are out of specification.

Required Tools

Illustration 1	g06329379
Tooling (T1) 198-4240 Digital Pressure Indicator Gp

Illustration 2	g06329296
(T2) 418-3611 Track Block

Test Preparation

1. Position the machine on level ground.

2. Stop the engine.

3. Release the pressure in the hydraulic system. Refer to Operation and Maintenance Manual , "System Pressure Release".
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   Illustration 3	g06180512
   Pump compartment (1) Pressure tap (delivery pressure for pump 1) (2) Pressure tap (delivery pressure for pump 2)

4. Connect pressure sensor (T1b) to pressure tap (1). Use this pressure sensor to monitor the crossover relief valve pressure setting of the right travel motor.

5. Connect pressure sensor (T1b) to pressure tap (2). Use this pressure sensor to monitor the crossover relief valve pressure setting of the left travel motor.
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   Illustration 4	g06433230
   Sprocket (left forward travel) (T2) Track block (3) Sprocket

6. Place track block (T2) in sprocket (3) to block forward left travel.

Test Procedure

Note: A temporary setting of the main relief valve is required before any line relief valves can be adjusted.

Note: Pressure values in Table 5 are approximate values. Use a pressure gauge for adjustment.

Illustration 5	g06612306
Travel brake valve (left) (7) Crossover relief valve (reverse left travel) (8) Crossover relief valve (forward left travel)

1. Start the engine.

2. Place the hydraulic activation control lever in the UNLOCKED position.

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

4. Place the machine controls at the following settings: engine speed dial "7" and AEC switch OFF (if equipped).

5. Move the joystick for the stick until the stick is at the full STICK OUT position (full retraction of stick cylinder).

6. Check the main relief setting pressure setting at pressure tap (1) and pressure tap (2). The pressure setting should be 35000 + 500 - 1000 kPa (5076 + 73 - 145 psi).

7. Return the joystick to the NEUTRAL position.
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   Illustration 6	g06195051
   Main relief valve (A) Adjustment screw (L) Locknut

8. Loosen the locknut. Set the temporary main relief pressure to 37000 ± 500 kPa (5366 ± 73 psi). Turn the adjustment screw clockwise to increase the pressure. Turn the adjustment screw counterclockwise to decrease the pressure. Tighten the locknut.

   Note: Always make final pressure adjustments on pressure rise.

9. Verify the temporary main relief pressure setting with a second function. Move the joystick for the boom until the boom is at full BOOM RAISE position (full extension of the boom cylinder). The main relief pressure should be 37000 ± 500 kPa (5366 ± 73 psi).

10. Slowly move the left travel control lever to full FORWARD position.

11. Check the pressure setting of the left forward travel crossover relief.

12. Remove track block (T2) from sprocket (4).

13. Place track block (T2) in sprocket to block reverse left travel.

14. Slowly move the left travel control lever to full REVERSE position.

15. Check the pressure setting of the left reverse travel crossover relief.

16. To test the crossover relief valves on the right travel motor, place the track block (T2) in the sprocket for right travel. Use the pressure tap (1) to monitor the crossover relief valve pressure settings for the right travel motor.

17. If the pressure reading for the crossover relief valve is not above the service limit, replace the appropriate crossover relief valve.

18. Return the main relief valve pressure to the specified setting after crossover relief valve pressure setting is attained. Refer to Testing and Adjusting, "Relief Valve (Main) - Test and Adjust".