Usage:
990 (7HK),
990 Series II (4FR) Wheel Loaders
Reference: Service Manual Module, SENR6653, Systems Operation Testing & Adjusting 990 and 990 Series II Wheel Loader. This module is found in Service Manual SENR1365.
On Page 37 and 38, the procedure for recharging the ride control accumulator should be corrected to read as follows:
Ride Control Accumulator Recharging Procedure
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Make reference to WARNING on first page of Hydraulic System Testing And Adjusting section.
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Ride Control Accumulator Charging Valve Location (1) Control valve. (2) Charging valve. (3) Accumulator.
1. Move the machine to level ground.
2. Move transmission control lever to NEUTRAL. Move the transmission neutral lock into the LOCKED position.
3. Engage the parking brake.
4. Place the ride control switch in the ON position.
5. Raise the lift arms to the top of their travel and hold the control lever in the RAISE position for 5 seconds. (Holding the control lever in the RAISE position keeps the lift circuit at main relief valve setting and compresses the air in the accumulators).
6. Place the lift control lever in the NEUTRAL position.
7. Using the proper sized socket wrench, open each accumulator (3) gas charging valve (2) approximately one turn. This allows the compressed air to be released from the gas chamber of each accumulator.
8. After the air has been released, tighten the gas valves.
9. Lower the bucket to the ground and place the lift control lever in the FLOAT position. Leave the ride control switch in the ON position.
10. Remove the small cap on the charging valve assembly. Attach 7S-5439 Extension to each valve.
11. Attach nitrogen bottles to extensions and open valves to gauges on bottles. Open gas valves and charge the accumulators to 5000 ± 70 kPa (725 ± 10 psi).
12. Charge time should be 10-20 seconds.
13. If either or both gauges instantly go to 5000 kPa (725 psi), air has not been properly purged from the gas chamber(s). Repeat Steps 4 through 12.
14. When properly charged, close the valves on the nitrogen bottles, but leave the gauges connected to the accumulator.
NOTE: Leaving the gauge valves open ensures the accumulators pistons are at the bottom of there stroke and the chambers are full of nitrogen gas.
15. Check that the ride control switch is in the ON position.
16. Raise the lift arms to the top of their travel and hold the control lever in the RAISE position at main relief valve setting for 5 seconds. The gas pressure gauges should reach 11 000 to 15 200 kPa (1600 to 2200 psi).
NOTE: Low pressure indicates the accumulator(s) has not been fully charged. Repeat Steps 4 through 15.
17. Place the ride control switch in the OFF position.
18. Lower the bucket to the ground.
19. Place the ride control switch in the ON position. Gas pressure should drop immediately. This indicates the ride control is functioning properly.
NOTE: An empty bucket will have a tendency to raise.
20. If gas pressure does not drops to 5000 kpa (725 psi), repeat Steps 4 through 19.
21. Remove the gauges, gas bottles, extensions and chucks. Replace the charging valve caps.