D6R Series III Track-Type Tractor Hydraulic System Caterpillar

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Do not check for leaks with your hands. Pin hole (very small) leaks can result in a high velocity oil stream that will be invisible close to the hose. This oil can penetrate the skin and cause personal injury. Use cardboard or paper to locate pin hole leaks.

The operation checks can be used to find leakage in the system. The operation checks can find a valve that is failing. The operation checks can also find a pump or a motor that is failing. The speed of rod movement of the cylinders is a measure of the condition of the cylinders and the pump.

Raise and lower the blade and the ripper several times. Operate the tilt control valve until the tilt cylinder is fully extended and retracted several times. If equipped, operate the angle control valve until the angle cylinders are extended and retracted several times.

1. Watch the cylinders as the cylinders are extended and retracted. Movement must be smooth and regular.

2. Listen for noise from the pump.

3. Listen for the sound of the operation of the pressure limiter valves. The pressure settings of the pressure limiter valves are listed in Testing and Adjusting, "Pressure Limiter Valve - Test".

Tests for Cycle Times

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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 systems. In order to prevent possible injury, release the hydraulic system pressure before working on any fitting, hose, or hydraulic component. Lower all attachments to the ground before service is started. If the hydraulic system must be serviced, tested, or adjusted with the attachment in the raised position, the attachments 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.

All tests for cycle times are performed with the engine at high idle.

The oil in the hydraulic system must be SAE 10 at a temperature of 75° ± 3°C (167° ± 5°F) in order to get the correct results.

If test results are in agreement with the table the circuit is normal. Check the relief valve for the correct opening pressure. See Testing and Adjusting, "Main Relief Valve and Crossover Relief Valve - Test" in this module for the correct setting.

If only one of the cycle times is slow, check that circuit for cylinder drift.

Check these items if the cycle time is not correct.

1. Check the adjustment of the controls.

   ReferenceRefer to Specifications, "Hydraulic System" in this manual.

2. Check pump efficiency.

3. Check the setting of the relief valve.

4. Check the cylinders for leakage.

5. Check the makeup valves for leakage.

6. Check the pressure limiter valve.

7. The valve spools in the bulldozer control valves and in the ripper control valve could be worn.

Drift Tests for Bulldozer Lift Cylinders

Test

1. Raise the front of the machine off the ground by lowering a level blade. Put the control lever in the HOLD position. Shut off the engine and watch the lift cylinder rods for movement.

2. Raise the front of the machine off the ground by lowering a level blade. Shut off the engine. Hold the lift control lever in the LOWER position. Watch the lift cylinder rods for movement.

3. Raise the blade off the ground. Put the control lever in the HOLD position. Shut off the engine and watch the lift cylinder rods for movement.

4. Raise the blade off the ground. Shut off the engine. Hold the lift control lever in the RAISE position. Watch the lift cylinder rod for movement.

Results

Drift Tests for Bulldozer Tilt Cylinder

Tests

1. Position the blade flat on the ground. Raise the front of the machine off the ground by lowering the right side of the blade to the TILT RIGHT position. Put the tilt control lever in the HOLD position. Shut off the engine. Watch the tilt cylinder rod for movement.

2. Position the blade flat on the ground. Raise the front of the machine off the ground by lowering the right side of the blade to the TILT RIGHT position. Hold the tilt control lever in the TILT RIGHT position. Shut off the engine. Watch the tilt cylinder for movement.

3. Position the blade flat on the ground. Raise the front of the machine off the ground by lowering the left side of the blade to the TILT LEFT position. Put the tilt control lever in the HOLD position. Shut off the engine. Watch the tilt cylinder rod for movement.

4. Position the blade flat on the ground. Raise the front of the machine off the ground by lowering the left side of the blade to the TILT LEFT position. Hold the tilt control lever in the TILT LEFT position. Shut off the engine. Watch the tilt cylinder for movement.

Drift Tests for Ripper Lift Cylinder

Tests

1. Raise the ripper off the ground. Put the control lever in the HOLD position. Shut off the engine and watch the ripper cylinder rod drift.

2. Raise the ripper off the ground. Shut off the engine. Move the ripper lift control lever to the RAISE position. Watch the ripper cylinder rod drift.

Steering Checks

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Personal injury or death can result from sudden machine movement. Sudden movement of the machine can cause injury to persons on or near the machine. To prevent injury or death, make sure that the area around the machine is clear of personnel and obstructions before operating the machine.

Steering checks indicate when the operation of the steering circuit is normal. The sprocket speed checks and the steering turn checks will give an indication of steering circuit problems.

Steering Turn Diameter Check

Test

1. Move the machine to an open area that is flat and dry. The ground conditions must limit the amount of track slip when the machine is turning. Check that the steering linkage is correctly adjusted.

2. Start and run the machine at high idle. Raise all of the implements to a full RAISE position.

3. Release the parking brake. Put the transmission in FIRST SPEED FORWARD.

4. Move the tiller handle to the full STEER LEFT POSITION.

5. Make a full turn of 360 degrees.

6. Stop the machine after the full turn. Lower all of the implements to the ground. Stop the engine.

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Illustration 1	g00500963
Steering check (A) Diameter of the turn

7. Measure distance (A) . See Illustration 1. Distance (A) should be 1.8 to 2.3 m (5.9 to 7.5 ft).

8. Do Steps 1 through 7 again with the tiller handle in the full STEER RIGHT POSITION.

9. Do Steps 1 through 6 again with the tiller handle in the full STEER RIGHT POSITION and in the full STEER LEFT POSITION. Hold the bulldozer control lever in the full RAISE position.

10. Measure distance (A) . See Illustration 1. Distance (A) should be 4.8 to 6.0 m (16 to 20 ft).

Results

If distance (A) is too long after Steps 1 through 8, check the steering linkage, the implement hydraulic pump, the steering motor, the steering control valve and the counterbalance valve for correct operation.

If distance (A) is too long after Steps 9 through 10, check the priority flow control valve in the steering control valve.

If a problem is indicated by the checks, use the Testing and Adjusting, "Steering Hydraulic Circuit - Test" in order to determine the specific problem.

Sprocket Speed Difference

Test

Note: This check should be done primarily after machine repair or machine rebuilding.

1. Move the machine to a clear area that is level. Lower the implements to the ground. Stop the engine.

2. Separate the tracks. Remove the tracks from the sprockets on the final drives.

   ReferenceDisassembly and Assembly, RENR8173, "D6R Series III Track-Type Tractor Power Train"

3. Before you do the checks, make sure that the steering linkage is correctly adjusted. Mark the sprockets of both final drives in order to count the revolutions during the checks.

4. Start the engine. Run the engine at high idle.

5. Release the parking brake. Move the tiller handle to the stop in the STEER RIGHT position. Keep the transmission to the NEUTRAL position.

6. This step checks the oil flow through the steering system. Use a stopwatch to accurately count the number of revolutions per minute of each sprocket. Add the rpm of the right sprocket to the rpm of the left sprocket. The sum of the rpm of the left sprocket and the right sprocket should be 22.5 ± 1.1 rpm.

   Example

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   Table 10

   A Check of the Sprocket Speeds for Steering Oil Flow
   Rpm of left sprocket		12.5 rpm
   Add rpm of right sprocket.	+	10.5 rpm
   Sum of the rpm of the sprockets	=	23.0 rpm

7. Move the tiller handle to the full STEER LEFT POSITION. Do Steps 5 and 6 again. The sum of the speeds between the left sprocket and the right sprocket should be 22.5 ± 1.1 rpm.

8. When the checks, the tests and any needed adjustments are completed, stop the engine. Remove all test equipment. Connect the track.

Results

If the sprocket speeds are not within the tolerances, check the component operation: hydraulic pump, steering motor, control valve and counterbalance valve.

If Step 6 is low, check these causes: engine speed, leaks in the signal circuit and the priority flow control valve in the steering control valve.

If Step 6 is high, check the adjustments of the priority flow control valve and the pressure and flow compensator valve on the pump.

If a problem is indicated by the checks, use the Testing and Adjusting, "Steering Hydraulic Circuit - Test" in order to determine the specific problem.