SPOOL 8E3055 - Caterpillar

Procedure for Releasing Pressure
The release of hydraulic pressure in all hydraulic circuits before any service is performed.
Illustration 1 g00666865
Position the machine on level ground.
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 bucket is flat on the ground.
Shut off the engine.
Turn the engine start switch to the ON position without starting the engine.
Push the left console downward into the LOCKED position.
Move only the joysticks or the pedals of the hydraulic circuit that requires service to the FULL STROKE positions. Movement of the joysticks will release the high pressure only in that single hydraulic circuit. This will also release any pressure that might be present in the pilot hydraulic circuit.Note: For the hydraulic circuit that requires the activation of a switch for operation, activate the necessary switches for the operation of the hydraulic circuit.
After releasing the hydraulic pressure of the hydraulic circuits, pull the left console, or the hydraulic lockout control into the UNLOCKED position.
Turn the engine start switch to the OFF position.
Slowly loosen the filler plug on the hydraulic tank and release the pressure. Leave the filler plug loose for a minimum of 45 seconds. This will release the pressure that may be present in the return hydraulic circuit.
Hand tighten the filler plug on the hydraulic tank.
The pressure in the hydraulic circuits is now released and lines and components can be disconnected or removed.