When the main pumps have been serviced or the hydraulic oil has been replaced, remove the air from the hydraulic system. Remove the air from the hydraulic system in the following manner:
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, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat® products.
Dispose of all fluids according to local regulations and mandates.
Personal injury can result from hydraulic oil pressure and hot oil.
Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system.
Make sure all of the work tools have been lowered to the ground, and the oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.
(1) Vent plug.
- When the engine is stopped, remove vent plug (1) from the top of the main pump. Leave vent plug (1) out for several minutes until the main pumps are filled with hydraulic oil. When the pumps are filled with oil, tighten vent plug (1).
To avoid system damage, make sure that the hydraulic pump is properly filled with hydraulic oil before start-up.
- Start the engine and run the engine at low idle. Raise the boom and hold the boom in the RAISED position.
- Stop the engine. Lower the boom slowly until the bucket is on the ground. The hydraulic tank is now under pressure.
- Slowly loosen vent plug (1). Loosen vent plug (1) until hydraulic oil flows out of the opening for vent plug (1).
- Tighten vent plug (1).
Note: Hydraulic oil pressure can accumulate in the boom cylinder lines if the machine has boom lowering control valves. For information on relieving the hydraulic oil pressure, refer to Operation and Maintenance Manual, "Equipment Lowering with Engine Stopped".