992G Wheel Loader Electrohydraulic System Caterpillar

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Sudden movement or accidental starting of the machine can cause personal injury or death to persons on or near the machine. To prevent personal injury or death, perform the following: Park the machine on a smooth, level surface. Lower the bucket and/or attachments to the ground and engage the parking brake. Stop the engine and remove the key. Block the wheels and install the steering frame lock.

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Personal injury or death can result from sudden movement of the lift cylinders or the tilt cylinders. Do not stand under the work tool when you are testing or adjusting the lift cylinders or the tilt cylinders. Do not stand under the lift arms when you are testing or adjusting the lift cylinders or the tilt cylinders.

The ride control valve can be the cause of excessive lift cylinder drift. This procedure will isolate the ride control valve from the head end of the lift cylinders. When you perform the lift cylinder drift test, isolate the ride control valve from the hydraulic system.

Illustration 1	g01057315
Main Control Valve Group Location of the Ball Valve (Manual Lower)

Note: Before testing the machine for drift, ensure that the ball valve (manual lower) is blocking the flow of pilot oil to the hydraulic tank. The ball valve is located in the loader frame at the articulation hitch.

1. Connect the steering frame lock link.

2. Lower the bucket to the ground.

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Illustration 2	g01056127
Location of the Switch (Hydraulic Lockout)

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Illustration 3	g01056128
Location of the Switch (Ride Control)

3. Release the pressure in the implement hydraulic system and in the ride control system. Do not start the engine. Turn the engine start switch to the ON position. Move the switch (hydraulic lockout) to the UNLOCKED position. Move the switch (ride control) to the ON position. Move the lift control lever and the tilt control lever through all positions. Turn the engine start switch to the OFF position.

   Reference: For additional information about releasing the pressure in the implement hydraulic system, refer to the Service Manual Testing and Adjusting, SENR1367, "System Pressure - Release" for the machine that is being serviced.

4. Push in the plunger on the breaker relief valve on the implement hydraulic tank in order to relieve the pressure in the implement hydraulic tank. Hold the plunger in position until all pressure is released from the implement hydraulic tank.

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Illustration 4	g01056018
Right Side View of the Loader Frame (1) Non-engine end frame (NEEF). (2) Ride control valve. (3) Hose assembly. (4) Manifold (main control valve). (5) Ride control accumulators.

5. Remove hose assembly (3) that is between the ride control valve and the manifold (main control valve).

   Note: The ride control valve is located in the non-engine end frame (NEEF) at the articulation joint.

6. Install a 5H-4019 Cover and a 4F-7391 Seal on the ride control valve at the location of the hose assembly (1). Use two 8C-3206 Half Flanges, four 8T-4196 Bolts, and four 8T-4121 Hard Washers to hold the cover to the ride control valve.

7. Install a 6V-9833 and a 5K-9090 Seal on the opposite end of the hose assembly. Use two 6V-9833 Cap to hold the tube assembly. The tube assembly is connected to the lift function (head end) on the manifold for the main control valve (4) .

8. The previous step isolates the ride control valve from the main control valve. This eliminates the ride control valve from affecting the test.

9. If isolating the ride control valve eliminated the drift problem, inspect the ride control valve. Check for scoring in the main valve stem and in the valve body. Check for O-rings that are cut or missing from the solenoid valve.

10. When the testing is complete, remove the covers, caps, and plugs. Install hose assembly (3) .