651E and 657E Wheel Tractor-Scrapers Hydraulic System Relief Valve (Push-Pull) - Test and Adjust Caterpillar

Before you begin the following procedure, refer to Testing and Adjusting, "Machine Preparation for Troubleshooting".

Perform the test and any necessary adjustments to the BAIL RAISE pressure setting first. When the BAIL RAISE pressure setting of the relief valve has been corrected, the BAIL DOWN pressure setting will be set automatically.

Procedure for BAIL RAISE Pressure Setting

Illustration 1	g00737231
Cylinder Lines for the Bail (1) Line to rod end of bail cylinder (2) Line to head end of bail cylinder

1. Operate the machine until the hydraulic oil reaches normal operating temperature.

2. Stop the machine on a hard, level surface. Move the transmission control lever to NEUTRAL. Lower the bowl. Stop the engine. Engage the parking brake.

3. Disconnect line (1) from the connector at the rod end of the bail cylinder.

4. Assemble the following components and connect to the open ports: 6V-9837 Swivel Tee, 3E-7423 Connector, 5P-1838 O-Ring Adapter, 3B-7722 Pipe Bushing and 6V-3966 Fitting As .

5. Assemble the following components and connect to 6V-3966 Fitting As : 6V-4143 Coupler, 177-7861 Hose As, 8T-4188 Union Adapter and 8T-0851 Pressure Gauge (0 to 16,000 kPa (0 to 2,300 psi)).

6. Start the engine. Run the engine at HIGH IDLE in NEUTRAL.

7. Move the bail control switch to the BAIL RAISE position. The reading on the pressure gauge should be 7600 ± 350 kPa (1102 ± 51 psi).

8. If the pressure setting requires adjustment, continue to Step 9. If the pressure setting is correct, continue to Step 13.

9. If it is necessary to change the setting of the relief valve for the bail, stop the engine.

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Illustration 2	g00655475
Section View of Push-Pull Control Valve (3) Relief valve (4) Piston (5) Shims

10. Remove relief valve (3) from the push-pull control valve. Check that piston (4) is free and does not stick. Remove shims (6) in order to decrease the pressure setting of the push-pull control valve. Add shims (6) in order to increase the pressure setting of the push-pull control valve. Refer to Table 2 for the pressure change of the shims.
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    Table 2

    Chart for Shims
    Part Number	Thickness	Pressure Change for One Shim
    3H-2549	0.25 mm (0.010 inch)	190 kPa (28 psi)

11. Install relief valve (3) .

12. Repeat Steps 6 through 8.

13. Stop the engine. Remove all test equipment.

14. Connect line (1) to the connector at the rod end of the bail cylinder.

Procedure for BAIL DOWN Pressure Setting

15. Operate the machine until the hydraulic oil reaches normal operating temperature.

16. Stop the machine on a hard, level surface. Move the transmission control lever to NEUTRAL. Lower the bowl. Stop the engine. Engage the parking brake.

17. Disconnect line (2) from the elbow at the head end of the bail cylinder.

18. Assemble the following components and connect to the open ports: 6V-9837 Swivel Tee, 3E-7423 Connector, 5P-1838 O-Ring Adapter, 3B-7722 Pipe Bushing and 6V-3966 Fitting As .

19. Assemble the following components and connect to 6V-3966 Fitting As : 6V-4143 Coupler, 177-7861 Hose As, 8T-4188 Union Adapter and 8T-0856 Pressure Gauge (0 to 6,000 kPa (0 to 870 psi)).

20. Start the engine. Run the engine at HIGH IDLE in NEUTRAL.

21. Move the bail control switch to the BAIL DOWN position. The reading on the pressure gauge should be 3900 ± 350 kPa (566 ± 51 psi).

22. If the pressure setting for the BAIL RAISE has been adjusted, the BAIL DOWN pressure will automatically be correct. If the pressure is incorrect, check relief valve (3) in order to ensure that piston (4) moves freely. Refer to Steps 9 through 11 for more information.

23. Stop the engine. Remove all test equipment.

24. Connect line (2) to the elbow at the head end of the bail cylinder.