966F Wheel Loader and 966F Series II Wheel Loader Hydraulic System Caterpillar

Show/hide table

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 work tool to the ground and engage the parking brake. Stop the engine and remove the key. Block the wheels and install the steering frame lock.

Show/hide table

Personal injury or death can result from machine articulation or movement. Machine frames can move and a person can be crushed. Connect the steering frame lock link between the front and rear frames before working on machine. Secure clevis pin with locking pin. Before operating the machine, fasten the steering frame lock link into the stored position and secure the clevis pin with locking pin. Failure to lock into the stored position before operating can result in loss of steering.

This test will check the drift rate of the lift cylinders. The drift rates will change according to many conditions (hydraulic oil temperature, type of bucket, load in the bucket, etc). The values in the table are for an empty bucket.

Lift Cylinder

1. Move the machine to an open area so that the bucket can be fully raised.

2. Engage the parking brake.

3. Move the steering frame lock to the locked position.

4. Move the transmission direction control to the NEUTRAL position.

5. Start the engine. Warm the hydraulic oil to normal operating temperature of approximately 54° to 82°C (129° to 180°F).

6. Actuate the lift cylinders up and down for five repetitions. This will help to ensure that there is warm oil in the lift cylinders.

7. Raise the bucket until the lift cylinders are fully extended. Move the lift control lever to the HOLD position.

   Note: Do not engage the implement lockout feature during the drift test.

8. Stop the engine.

9. Check the distance of rod movement according to the following chart.
   Show/hide table

   Table 1

   Approximate Lift Cylinder Drift
   Oil Temperature	Maximum Drift	Time
   38° to 49°C (100° to 121°F)	13.0 mm (.51 inch)	5.0 minutes
   50° to 65°C (122° to 149°F)	13.0 mm (.51 inch)	2.7 minutes
   66°C (150°F) or more	13.0 mm (.51 inch)	1.7 minutes

10. If the amount of cylinder drift is within the specification, this lift circuit is not causing a drift problem.

11. If there is too much drift, check the check valves and check the makeup valves. Isolate the lift cylinders and check the lift cylinders for drift.

    Reference: For additional information about lift cylinder drift, refer to the Service Manual module Testing and Adjusting, "Lift Cylinder - Isolation and Drift Check" for the machine that is being serviced.

12. Start the engine. Lower the bucket to the ground. Stop the engine.

Tilt Cylinder

1. Move the machine to an open area so that the bucket can be fully raised.

2. Engage the parking brake.

3. Move the steering frame lock to the locked position.

4. Move the transmission direction control to the NEUTRAL position.

5. Start the engine. Warm the hydraulic oil to normal operating temperature of approximately 54° to 82°C (129° to 180°F).

6. Actuate the tilt cylinder in and out for five repetitions. This will help ensure that there is warm oil in the tilt cylinder.

7. Raise the bucket until the lift cylinders are fully extended. Position the bucket so that the bottom of the bucket is parallel to the ground. Move the tilt control lever to the HOLD position.

   Note: Do not engage the implement lockout feature during the drift test.

8. Stop the engine.

9. Check the distance of rod movement according to the following chart.
   Show/hide table

   Table 2

   Approximate Tilt Cylinder Drift
   Oil Temperature	Maximum Drift	Time
   38° to 49°C (100° to 121°F)	19.0 mm (.75 inch)	5.0 minutes
   50° to 65°C (122° to 149°F)	19.0 mm (.75 inch)	2.7 minutes
   66°C (150°F) or more	19.0 mm (.75 inch)	1.7 minutes

10. If the amount of cylinder drift is within the specification, this tilt circuit is not causing a drift problem.

11. If there is too much drift, check the check valves and check the makeup valves. Isolate the tilt cylinders and check the tilt cylinders for drift.

    Reference: For additional information about tilt cylinder drift, refer to the Service Manual module Testing and Adjusting, "Tilt Cylinder - Isolation and Drift Check" for the machine that is being serviced.

12. Start the engine. Lower the bucket to the ground. Stop the engine.

Note: Auxiliary cylinders will drift in the CLOSE (LOWER) direction because of an orifice in the rod end line. The orifice connects to the tank.