SPROCKET & HUB 8C7864 - Caterpillar

Release of Hydraulic Pressure from the Main Hydraulic System
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.
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.
Perform the following steps to release the hydraulic system pressure from the main hydraulic system.Note: For additional safety, wrap hydraulic joint with material that could absorb/reduce any residual pressure of oil when released. Loosen the joint slowly, pause, and carefully check hydraulic joint for tensions indicating presence of pressure or spring force in lines or components.
Position the machine on level ground.
Illustration 1 g06185115
Fully retract the stick cylinder rod. Adjust the position of the bucket so that the bucket is parallel to the ground. Lower the boom until the work tool is flat on the ground. Refer to Illustration 1.
Release the system pressure from the implement and swing hydraulic circuits.Note: Perform Step 3.b through Step 3.d immediately after the engine is shut off to insure adequate pilot system pressure is available to release the pressure in the hydraulic circuits.
Shut off the engine.
Turn the engine start switch to the ON position without starting the engine.
Place the hydraulic activation control lever in the UNLOCKED position.
Illustration 2 g06184822
Move both joysticks in a circular motion to the FULL STROKE positions multiple times until the pilot accumulator has been exhausted.Note: Pilot pressure is required to relieve hydraulic system pressure.
Place the hydraulic activation control lever in the LOCKED position.
Start the engine to recharge the pilot accumulator.Note: Do not activate any controls when recharging the pilot accumulator.
Shut off the engine.
Repeat Step 3.b through Step 3.g until the high-pressure lines have been released.Note: Each time the accumulator is recharged, start the joysticks at different positions or rotate in the reverse direction. Doing so will ensure that the same circuit is not being relieved each time.Note: You can also move only the joysticks or pedals of the hydraulic circuit that requires service to the full stroke positions after moving joysticks in a circular motion multiple times. This action will release the high pressure only in that single hydraulic circuit. This action will also release any pressure that might be present in the pilot hydraulic circuit.
Release hydraulic system pressure in the attachment