D350E Series II and D400E Series II Articulated Trucks Steering, Suspension, and Body Hoist Hydraulic Systems Caterpillar

Show/hide table

Dry nitrogen is the only gas approved for use in the accumulator. Charging the accumulator with oxygen gas will cause an explosion. This danger will not happen if nitrogen cylinders with standard CGA (Compressed Gas Association, Inc.) Number 580 connections are used. When you order nitrogen gas, be sure that the cylinders are equipped with CGA No. 580 Connections. Do not use color codes or other methods of identification to tell the difference between nitrogen and oxygen cylinders.

Show/hide table

Read all Warning labels on the suspension cylinders before servicing. The machine must be on level ground before releasing the nitrogen pressure. Do not check the oil in the suspension cylinder until all of the nitrogen pressure has been released. Do not remove valves, covers, or plugs from the cylinder unless the rod is fully retracted and all of the nitrogen pressure as been released. Stand clear of the machine during suspension cylinder charging, discharging, or testing and adjusting procedures, or while lifting or lowering the machine. Sudden movement upward or downward can cause clearance to change rapidly. Failure to heed this Warning could lead to injury or death.

Checking Precharge on the Machine

Use 7S-5437 charging equipment in order to check and adjust the nitrogen precharge.

1. Stop the machine on hard, level ground. Move the transmission control to the neutral position. Engage the parking brake. Stop the engine.

2. Install the steering frame locks. Block the trailer wheels and disengage the parking brake.

Show/hide table



Illustration 1	g00617568
Location of the manual shutoff valves

Show/hide table



Illustration 2	g00569707
The manual shutoff valves are located behind the cab. Open the transmission guard in order to access the manual shutoff valves. (1) Manual drain valve (2) Manual shutoff valve

3. Open manual drain valve (1) and slowly open manual shutoff valve (2). This connects the cylinders and the accumulator to the tank. This will cause the suspension to lower.

4. Leave manual drain valve (1) and manual shutoff valve (2) in the open position.

Show/hide table



Illustration 3	g00509607
7S-5437 Charging Equipment (3) Pressure gauge (4) Connection (5) Regulator (6) Valve (7) Pressure gauge (8) Adjusting screw (9) Valve (10) Connector

Show/hide table



Illustration 4	g00619044
Location of the suspension accumulator

Show/hide table



Illustration 5	g00569719
The suspension accumulator is located behind the cab. (11) Guard (12) Protective cap (13) Gas valve

5. Remove guard (11) and remove protective cap (12) from accumulator gas valve (13) .

6. Use the 0 to 14000 kPa (0 to 2000 psi) gauge (7) .

7. Make sure that valve (6) is closed.

8. Attach connector (10) to accumulator gas valve (13) .

9. Turn valve (9) clockwise until you encounter the stop. Gauge (7) will indicate the nitrogen gas pressure of the accumulator. The pressure must be 2070 ± 172 kPa (300 ± 25 psi).

10. If the pressure is high, remove the coupler at valve (6). Open valve (6) slightly In order to allow the pressure to decrease. Close valve (6) when the gauge reads the correct pressure.

11. If the pressure is low, attach regulator (5) to the nitrogen cylinder with connection (4) .

12. Close valve (6). Open the nitrogen cylinder valve and adjust screw (8) until gauge (3) reads the correct pressure.

13. Open valve (6) and allow the accumulator to charge.

14. The accumulator is charged correctly when both gauges match. Repeat steps 12 and 13 until the gauge readings match.

15. Close valve (6) and close the nitrogen cylinder valve.

16. Turn valve (9) counterclockwise until you encounter the stop. Remove the test equipment.

17. Close manual drain valve (1) and manual shutoff valve (2) .

18. Stop the engine. Engage the parking brake. Remove the wheel blocks.

19. Apply soapy water to accumulator gas valve (13) and check for leaks. If there is no leak, install protective cap (12) and install guard (11) .

20. Set the front suspension height. See Testing and Adjusting, "Suspension Height (Front) - Adjust".

21. Check the hydraulic oil level and add oil if it is necessary.

22. Remove the steering frame locks.

Charging a Rebuilt Accumulator

It is necessary to remove all air from the nitrogen chamber of the accumulator. When the accumulator is rebuilt, put 0.5 L (0.5 qt) of hydraulic oil in the nitrogen chamber. This oil is used to vent air from the accumulator and this oil is used to lubricate the piston top seal.

Use 7S-5437 charging equipment :

Show/hide table



Illustration 6	g00617568
Location of the manual shutoff valves

Show/hide table



Illustration 7	g00569707
The manual shutoff valves are located behind the cab. Open the transmission guard in order to access the manual shutoff valves. (1) Manual drain valve (2) Manual shutoff valve

1. Install the accumulator on the machine. Make sure that the wheels are installed. The suspension cylinders must be retracted. (The suspension must be lowered.) See "Checking Precharge on the Machine" for the procedure on lowering the suspension. Manual drain valve (1) must be closed. Manual shutoff valve (2) must also be closed. Install the steering frame locks and block the rear wheels. Do not charge the accumulator until all of these conditions are met.

Show/hide table



Illustration 8	g00509607
7S-5437 Charging Equipment (3) Pressure gauge (4) Connection (5) Regulator (6) Valve (7) Pressure gauge (8) Adjusting screw (9) Valve (10) Connector

Show/hide table



Illustration 9	g00619044
Location of the suspension accumulator

Show/hide table



Illustration 10	g00569719
The suspension accumulator is located behind the cab. (11) Guard (12) Protective cap (13) Gas valve

2. Remove guard (11) and remove protective cap (12) from the accumulator gas valve (13) .

3. Use the 0 to 14000 kPa (0 to 2000 psi) gauge (7) .

4. Make sure that valve (6) is closed. Attach connector (10) to accumulator gas valve (13) .

5. Turn valve (9) clockwise until you encounter the stop. Gauge (7) will indicate the nitrogen gas pressure of the accumulator.

Show/hide table

NOTICE
Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Caterpillar Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on Caterpillar products. Dispose of all fluids according to local regulations and mandates.

6. Disconnect the coupler at valve (6). Close valve (6) and secure valve (6) in a suitable container.

7. Start the engine and move the hoist lever to the lower position.

8. Open shutoff valve (2) and allow the suspension to rise fully. Open valve (6). This will vent air and excess oil from the gas chamber of the accumulator.

9. Close valve (6) .

10. Move the hoist lever to the float position. Open manual drain valve (1) and slowly open manual shutoff valve (2). This connects the cylinders and the accumulator to the tank. This will cause the suspension to lower.

11. Close manual drain valve (1). Move the hoist lever to the hold position. Move the hoist lever to the lower position. The suspension should fully raise. Close manual shutoff valve (2) .

12. Repeat steps 10 and 11 five times. This should remove any air from the system.

13. Make sure that the suspension is fully lowered. Attach a hose to the bleed fitting of the accumulator and secure the free end in a suitable container. The bleed fitting of the accumulator is located at the base of the accumulator.

14. Attach the coupler to valve (6). Attach regulator (5) to the nitrogen cylinder.

15. Close valve (6). Open the nitrogen cylinder valve and adjust screw (8) until gauge (3) reads the correct precharge pressure. The pressure must be 2070 ± 172 kPa (300 ± 25 psi).

16. Open valve (6) until the accumulator is charged. As the accumulator charges, the piston will move to the bottom of the accumulator. This will vent air from the oil chamber of the accumulator and oil will flow from the bleed fitting. Remove the hose when oil stops flowing.

17. The accumulator is charged correctly when both gauges agree. Repeat step 15 through step 17 if it is necessary.

18. Close valve (6) and close the nitrogen cylinder valve.

19. Turn valve (9) counterclockwise until you encounter the stop. Remove the test equipment.

20. Stop the engine. Engage the parking brake. Remove the wheel blocks.

21. Apply soapy water to accumulator gas valve (13) and check for leaks. If there is no leak, install protective cap (12) and install guard (11) .

22. Set the front suspension height. See Testing and Adjusting, "Suspension Height (Front) - Adjust".

23. Check the hydraulic oil level and add oil if it is necessary.

24. Remove the steering frame locks.

Charging a New Accumulator

A new accumulator should contain oil in the nitrogen chamber. The accumulator should be slightly charged with less than 350 kPa (50 psi) nitrogen.

Note: Be sure to check the nitrogen precharge of the accumulator before proceeding.

Show/hide table

The gas valve can blow out without warning if loosened while there is still nitrogen gas in the accumulator. This can cause personal injury. Do not attempt to remove the gas valve untill all nitrogen gas pressure has been released.

Charge a new accumulator in the same way as a rebuilt accumulator. See "Charging a Rebuilt Accumulator". A small amount of oil should be expelled during step 8. If no oil is expelled during step 8, it is necessary to add oil to the nitrogen chamber. This will ensure that all air is vented and the piston top seal receives adequate lubrication.

Note: The piston must be moved away from the top of the cylinder before oil will pass through the gas valve.