- Boom hydraulic circuit
- Stick hydraulic circuit
- Tool tilt hydraulic circuit
- Felling head hydraulic circuit
- Swing hydraulic circuit
- Travel hydraulic circuit
- Pilot hydraulic circuit
- Return hydraulic circuit
Release Of Hydraulic Pressure From The Hydraulic System
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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. |
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| NOTICE |
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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, "Caterpillar Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on Caterpillar products. Dispose of all fluids according to local regulations and mandates. |
Perform the following steps in order to release the hydraulic pressure from multiple hydraulic circuits of the main hydraulic system.
- Position the machine on level ground.
- Fully retract the stick cylinder rod. Adjust the position of the felling head so that the felling head is vertical to the ground. Lower the boom until the felling head is resting on the ground.
- 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.
- Move only the joysticks or the pedals of the hydraulic circuit that requires service to the FULL STROKE positions. This will release the high pressure only in that hydraulic circuit. This will also release any pressure that might be present in the pilot hydraulic circuit.
Note: If the hydraulic circuit that requires service requires the activation of a switch for operation, activate the necessary switches for the operation of the hydraulic circuit.
- Place the hydraulic activation control lever in the LOCKED position.
- Start the engine.
- Place the hydraulic activation control lever in the UNLOCKED position. Do not move any joysticks or pedals from the NEUTRAL position during this step. Do not activate any switches during this step.
- Return the hydraulic activation control lever to the LOCKED position.
- Shut off the engine.
- Repeat Steps 4 through 11 for each additional hydraulic circuit that requires service.
- After releasing the hydraulic pressure in each of the desired hydraulic circuits, place the hydraulic activation control lever in the LOCKED position.
- Turn the engine start switch to the OFF position.
- Open the cover for the engine compartment.
- Press the hydraulic tank relief valve until all the pressure is released from the hydraulic tank.
- Slowly loosen the filler cap on the hydraulic tank and release the pressure. Leave the filler cap loose for a minimum of 45 seconds. This will release the pressure that may be present in the return hydraulic circuit.
- Tighten the filler cap on the hydraulic tank to the specified torque.
- The pressure in the multiple hydraulic circuits that require service is now released and lines and components can be disconnected or removed from those hydraulic circuits.