TK711, TK721, TK722 and TK732 Track Feller Bunchers Hydraulic System System Pressure - Release Caterpillar


System Pressure - Release
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1.1. Release Of Hydraulic Pressure From The Hydraulic System

The release of hydraulic pressure in a hydraulic circuit is required before service is performed to that hydraulic circuit. Release the pressure in the following hydraulic circuits before any hydraulic lines are disconnected or removed from that hydraulic circuit.

  • Boom hydraulic circuit

  • Stick hydraulic circuit

  • Tool tilt hydraulic circuit

  • Swing hydraulic circuit

  • Felling head (hydraulic circuit)

  • Harvester head (hydraulic circuit)

  • Travel hydraulic circuit

  • Leveling (hydraulic circuit)

  • Pilot hydraulic circuit

  • Return hydraulic circuit

Release Of Hydraulic Pressure From The Hydraulic System

------ WARNING! ------

Personal injury can result from contact with hot hydraulic oil and from contact with hydraulic oil that is under high pressure.

Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. The hydraulic oil pressure must be released before any service on the hydraulic system is performed or serious personal injury could occur.

Verify that all of the work tools have been completely lowered to the ground. Release the hydraulic oil pressure at the hydraulic tank through the breaker relief valve when the breaker relief valve is cool enough to touch with your bare hand. Verify that the hydraulic oil is cool before you begin to remove any hydraulic components or hydraulic lines.

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NOTICE

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, "Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids.

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.

  1. Position the machine on level ground.

  1. 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.

  1. Shut off the engine.

  1. Turn the engine start switch to the ON position without starting the engine.



    Illustration 1g00827520

    Hydraulic lockout control on early machines




    Illustration 2g01162811

    Hydraulic lockout control on later machines

  1. Place the hydraulic lockout control in the UNLOCKED position.

  1. 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.




    Illustration 3g00827465

    Hydraulic lockout control on early machines




    Illustration 4g01162814

    Hydraulic lockout control on later machines

  1. Place the hydraulic lockout control in the LOCKED position.

  1. Repeat Steps 4 through 7 for each additional hydraulic circuit that requires service.



    Illustration 5g01052558

    Layout of the cab on early machines




    Illustration 6g01162235

    Layout of the cab on later machines




    Illustration 7g01074453

  1. Open the hood for the engine compartment.

    Note: The switch for the hood is located underneath the right armrest on early machines. On later machines, the switch for the hood is located on the right hand console.

  1. Turn the engine start switch to the OFF position.



    Illustration 8g00941919

  1. Press the hydraulic tank relief valve that is located on the side of the hydraulic tank until all the pressure is released from the hydraulic tank.

  1. 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.

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