PLATE 2G7908 - Caterpillar

Machine Preparation for Troubleshooting
Move the machine to a smooth horizontal location. Move away from working machines and personnel. Lower the work tools to the ground.
Allow only one operator on the machine. Keep all personnel away from the machine or in the view of the operator.
Engage the parking brake.
Illustration 1 g00893065
Typical example
Place the steering frame lock in the LOCKED position.ReferenceFor more information about preparing the machine for troubleshooting, refer to the Service Manual module Testing and Adjusting, "Machine Preparation for Troubleshooting" for the machine that is being serviced.Pilot Oil Accumulator
The following procedure can be used in order to test the pilot oil accumulator. The pilot oil accumulator maintains pressure in the pilot hydraulic system. The accumulator allows you to lower the boom, and the work tools with a stopped engine.When you test or you charge the pilot oil accumulator, the pressure in the pilot hydraulic system must be released. The temperature of the nitrogen gas must also be taken into account. The pressure and volume of nitrogen gas varies with temperature.Operational Test for the Pilot Oil Accumulator
Table 2
Required Tools    
Part Number     Description     Quantity    
177-7860     Hose assembly     1    
8T-0856     Pressure Gauge     1    
Illustration 2 g01185771
Remove the front guard in order to access the main control valve.
Illustration 3 g03467679
Location of the pressure tap for pilot pressure
Install an 8T-0856 Pressure Gauge 4000 kPa (580 psi) on a 177-7860 Hose Assembly that has quick disconnect fittings. Install the other end of the hose to the pressure tap for the pilot pressure.
Start the engine and run the engine at HIGH idle. The pressure gauge will read 3515 345 kPa (510 50 psi).
Stop the engine. Turn the start switch to the ON position. Do not start the engine.
Move the implement control levers several times through the full range of travel. This process will relieve any pressure that may be present in the implement hydraulic system. Turn the key start switch to the OFF position.Note: For more