PUMP GP-YM 2423443 - Caterpillar

Sudden movement of the machine or release of oil under pressure can cause serious injury to persons on or near the machine.To prevent possible injury, perform the procedure that follows before testing and adjusting the hydraulic system.
Move the machine to a smooth horizontal location that is away from other machines and personnel. Lower all attachments to the ground.
Permit only one operator on the machine. Keep all other personnel away from the machine.
Engage the parking brake.
Stop the engine.
Move the hydraulic control levers to all positions so that the pressure in the hydraulic system is released.
Loosen the filler cap on the hydraulic tank so that the pressure in the tank is released.
Tighten the filler cap on the hydraulic tank.
The pressure in the system has now been released and lines or components can be removed. Follow the following procedure in order to define a problem with the hydraulic system. First, do Visual Checks. Next, do Operational Checks. Lastly, do Instrument Tests. This procedure helps identify hydraulic system problems. Once the problem is defined, go to Troubleshooting. The Troubleshooting Section lists the probable causes of a known problem. Since there may be more than one cause for a problem, the Troubleshooting Section may suggest performing specific inspections or specific instrument tests. These inspections and tests help identify the most probable causes.During a diagnosis of the hydraulic system, remember that correct oil flow, correct temperature, and correct pressure are necessary for correct operation.