938G Wheel Loader and IT38G Integrated Toolcarrier Machine Systems Caterpillar


System Pressure - Release

Usage:

IT38G 1CW

Release Procedure

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

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 attachments have been lowered, 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.


Hydraulic System

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

Hydraulic oil pressure can remain in the hydraulic system on this machine after the engine and pump have been stopped. Serious injury can result if this pressure is not released before any service is done on the hydraulic system. In order to prevent possible injury, release the hydraulic system pressure before working on any fitting, hose, or hydraulic component.

Lower all work tools to the ground before service is started. If the hydraulic system must be serviced, tested, or adjusted with the work tool in the raised position, the work tool and lift cylinders must be supported properly.

Always move the machine to a location away from the travel of other machines. Be sure that other personnel are not near the machine when the engine is running and tests or adjustments are being made.


  1. Park the machine on a hard, smooth, level surface. The location should also be dry and free of debris.

  2. Permit only one operator on the machine. All other personnel should be kept away from the machine.

  3. If the machine is equipped with a ride control system, place the ride control system into “Service”.mode. Refer to “Ride Control” in this Operation and Maintenance, "Operator Controls" section.


    Illustration 1g02727672

  4. Position the bucket or the work tool just above the ground at a slight downward angle. This position will ensure that the head end of the lift cylinders is pressurized.

  5. Engage the parking brake.

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

  7. When the engine has stopped, turn the engine start switch back to the ON position so the pilot oil can reach the main valve.

  8. Move the implement lockout switch to the UNLOCKED position.

  9. Move the lift control lever to the FLOAT position and the tilt control lever to the TILT BACK position at the same time. This action allows the bucket or the work tool to tilt back while the boom is lowered.

    The bottom of the bucket or the work tool should rest flat on the ground. The weight of the linkage should be supported by the ground. The pressure from the head end of the lift cylinders and from the ride control accumulator is now vented to the hydraulic tank.

  10. When the bucket or the work tool has settled to the ground, move both control levers to the HOLD position. Cycle the control levers through all positions several times in order to purge any remaining pressure from the implement hydraulic system. This action will completely drain the pilot accumulator.

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

  12. Slowly loosen the hydraulic tank filler cap in order to release the pressure from the hydraulic tank.

  13. After all of the pressure has been released, tighten the hydraulic tank filler cap. The hydraulic system pressure has now been released. Hydraulic lines and components can now be removed.

Release Procedure (Steering System, Braking System, and Quick Coupler) (If Equipped)

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

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. Park the machine on a hard, smooth, level surface. The location should also be dry and free of debris.

  2. Lower the bucket to the ground and stop the engine.

  3. Engage the parking brake.

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

  5. Turn the steering wheel fully to the left and fully to the right several times to relieve the pressure in the steering system.

  6. Depress the brake pedal repeatedly in order to release any pressure in the braking system. When no more resistance is felt and no pressure release is heard, the braking system, and Quick Coupler pressure is released.

  7. Slowly loosen the hydraulic tank filler cap in order to release the pressure from the hydraulic tank.

  8. After all of the pressure has been released, tighten the hydraulic tank filler cap. The hydraulic system pressure has now been released. Hydraulic lines and components can now be removed.

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