COVER 7N7825 - Caterpillar

Hydraulic System
Change Oil and Screen
1. Place the machine on level ground and lower the bucket to the ground with the stick vertical. 2. Open the access door on the right side of the machine.3. Clean the pump, hydraulic lines and hydraulic tank. 4. Relieve the internal pressure from the hydraulic tank by loosening the fill/vent plug. After the pressure is relieved, remove the plug. 5. The oil drain valve is located under the hydraulic tank.6. Remove the hydraulic tank access cover from under the upper structure. 7. Remove the oil drain valve plug. Refer to the General Hazard Information section for information on Containing Fluid Spillage.8. Install a pipe (with 1-11 ... 1/2 NPSM threads) and hose to open drain valve. Drain the oil into a container.9. Remove the pipe to close the drain valve.10. Inspect the O-ring. Replace the O-ring if it is worn or damaged.11. Clean and install the drain plug. 12. Remove the plug from the tube and allow the oil to drain into a container.13. Inspect the O-ring. Replace the O-ring if it is worn or damaged.14. Clean the plug. Install the plug and O-ring into the drain port.15. Install the access cover under the hydraulic tank. 16. Change the screen. Remove bolts (1), washers (2), and cover (3). Do not allow spring (4) to fall into the tank.17. Remove spring (4) and screen (5). Refer to the General Hazard Information section for information on Containing Fluid Spillage. 18. Inspect O-ring seals (6) and (7). Replace an O-ring if it is worn or damaged.19. Install the new screen. Follow step 17 and step 16 in reverse order to install screen (5). During installation, make sure the O-ring seals and spring are properly positioned.20. Fill the hydraulic system oil tank. See Lubricant Viscosities and Refill Capacities.21. Inspect the fill/vent plug O-ring for damage. Replace if necessary. Clean and install the fill/vent plug. 22. Remove the pressure cap.23. Inspect and clean the pressure cap. Replace it if it is damaged.24. Install the pressure cap. 25. When the hydraulic oil has been replaced, remove air from the hydraulic system as follows: Make no attempt to start the engine until the pump has been filled with hydraulic oil. Serious damage to the hydraulic components can result.* Disconnect drain hoses (1) and (2) from the main pump and swing pump. Add the hydraulic oil through the opening of the drain port of each pump. Inspect the O-ring. Replace the O-ring if it is worn or damaged. After filling each pump, connect drain hoses (1) and (2).* Start and run the engine at low idle to remove the air from the hydraulic system. * Remove the top cover of the main control valve compartment. * Slowly loosen each of the six air vent plugs (indicated by an arrow) until oil flows out of the plug opening. Tighten the plugs when oil flows free of bubbles. This is an indication that the air has been purged from the main