2003/05/19 Correction to Testing and Adjusting , "Ride Control Accumulator Recharging Procedure" {5077} Caterpillar

Wheel Loader:

990 Series II (S/N: 4FR1-UP)

990 (S/N: 7HK1-UP)

Testing and Adjusting, SENR6653, "990 Wheel Loader and 990 Series II Wheel Loader Hydraulic System", "Ride Control Accumulator Recharging Procedure". This module is part of Service Manual, SENR6640 or SENR1365.

A portion of the existing information is incorrect. Replace the steps with the following information. The remainder of the information is correct.

5. Remove the small cap on gas charging valve (2). Attach a 7S-5439 Extension Assembly to each gas charging valve (2) .

6. Install a chuck, hose assembly,the tee, and the needle valve assembly from the accumulator charging kit to gas charging valve (2) to each accumulator. Place the open end of the hose assembly away from the work area and away from other personnel.

7. Turn the valve handle on the chuck clockwise in order to open a path for the compressed nitrogen to flow from the gas chamber of each accumulator. Slowly, open the needle valve in order to allow the nitrogen gas charge from the accumulators.

8. After the nitrogen gas charge is purged, ensure that the needle valve is open all the way.

9. Place the ride control switch in the MANUAL position.

10. Raise the lift arms to the end of travel. Hold the lift lever in the RAISE position. This will ensure that all the nitrogen gas and trapped oil is released out of the accumulators.

11. Lower the work tool to the ground. Position the lift control lever to the FLOAT position.

12. Turn the engine start switch to the OFF position.

13. Place the key start switch to the ON position. Do not start the engine.

14. Position the lift control lever to the FLOAT position. Ensure that the detent holds the lift control lever in the FLOAT position.

    Note: The ride control switch should be in the MANUAL position.

15. Attach nitrogen charging cylinder and the remainder of the nitrogen charging group. Open the valves on the nitrogen charging cylinder to the gauges. Open the gas valves and charge the accumulators to 3445 ± 70 kPa (500 ± 10 psi).

    Note: The charging time for the accumulators should be 10 to 20 seconds.

16. If the gas gauge immediately goes to 3445 ± 70 kPa (500 ± 10 psi), the accumulators have not been purged properly. Repeat Step 6 through Step 15.

17. When the accumulators are properly charged, close the gas valves. Leave the gauge valve in the OPEN position.

    Note: With the gauge valves in the OPEN position, the accumulator pistons are at the bottom of the stroke. The chambers of each accumulator is full of nitrogen gas.

18. Raise the lift arms to the end of travel. Hold the lift control lever in the full RAISE position at the main relief valve setting until the pressure gauges reach 16535 kPa (2400 psi).

    Note: Low pressure indicates that the accumulators have not been charged fully. Repeat Step 6 through Step 15.

19. Lower the work tool to the ground. The gas pressure should drop immediately. This indicates that the ride control system is working properly.

20. If the gas pressure does not drop to 3100 kPa (450 psi), repeat Step 6 through Step 19.

21. After the ride control accumulators are charged properly, remove the nitrogen charging cylinder, extensions, and the nitrogen charging group.

22. Replace the small caps for the charging valves and the covers.