525D, 535D, 545D and 555D Wheel Skidders Caterpillar

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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.

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Personal injury or death can result from escaping fluid under pressure. Escaping fluid under pressure, even a very small pin-hole size leak, can penetrate body tissue and cause serious injury and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury. Always use a board or cardboard when checking for a leak.

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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.

This section provides probable causes to known problems. Since there may be several probable causes, specific inspections or instrument tests may be recommended. These inspections and tests will help to identify the causes that are most probable.

Grapple Controls

Illustration 1	g03679532

The right joystick (1) is on the right armrest of the seat (2). The buttons on the joystick control the grapple head rotation in a clockwise and counterclockwise direction. The buttons on the right joystick also control the grapple tong open and close operation.

Grapple Hydraulic System

The hydraulic system for the Clam Shell Grapple is divided into two separate circuits. One circuit is used to rotate the work tool and the other circuits is used to operate the shell assemblies

Illustration 2	g03375898
(1) Hydraulic cylinders (2) Relief valve (3) Relief valve (4) Swivel (5) Rotation Motor (6) Orifice (7) Check valve

Shell Circuit

The main components of the Clam Shell Grapple consist of the swivel (4) and the cylinders (1).

Swivel (4) is the center of the rotator assembly. The swivel provides the necessary transfer of hydraulic oil to the hydraulic cylinders in the Clam Shell Grapple. This transfer of oil allows the Clam Shell Grapple to rotate 360 degrees without damaging the hoses to the cylinders.

Double acting cylinders (1) provide the necessary force to operate the shells of the work tool effectively. The hydraulic circuit for the cylinders is independent from the circuit for rotation.

Illustration 3	g03375979
Illustration of Clam Shell in the CLOSED position (1) Hydraulic cylinders (4) Swivel (8) Line from the main pumps (9) Line to the main pumps

Illustration 3 demonstrates the operation of the work tool when the shells are opening. Oil flows from the host machine to line (9). The oil flows through swivel (4). The oil flows to the rod end of the cylinders (1). The oil pressure that is felt at the piston in the cylinder causes the cylinder to retract. This action opens the shells.

Oil from the head end of the cylinders returns to the hydraulic tank through line (8).

Rotation Circuit

The main components of the rotate circuit consist of the following components: swivel (4), relief valves (2) and (3), rotation motor (5), orifices (6), and check valves (7)

Rotate Circuit For Clockwise Rotation

Illustration 4	g03376186
(2) Relief valves (3) Relief valves (4) Swivel (5) Rotation motor (6) Orifice (7) Check valve (10) Line from the main pump (11) Line to the hydraulic tank

Hydraulic oil is supplied through line (10) to the grapple rotate circuit by the medium pressure pump that is located on the machine. The auxiliary control valve determines the direction of that the rotation motor (5) turns by diverting supply oil to either side of the rotation motor. return oil is sent back to the hydraulic tank through line (11).

Relief valves (2) and (3) prevent cavitation in the grapple rotate motor. The relief valves also prevent a shock load when the grapple rotate motor stops.

Hydraulic oil flow for the rotate circuit is restricted by orifices (6), and check valve (7).

Problem List

1. The oil temperature is too high.

2. There is a pause before pressure is reached in all circuits. All implement functions are sluggish.

3. The grapple moves while the grapple control lever is in the HOLD position.

4. The grapple droops when the grapple control lever is moved from the HOLD position to the UP position.

5. Line relief valves are noisy.

6. Too much drift in the grapple.

7. The cycle times for the arch, the boom, the tong, and the rotator are too slow.

8. The cycle times for the arch, the boom, the tong, and the rotator are too fast.

9. The grapple rotates too fast, or the grapple rotates too slowly.

Troubleshooting

Problem 1

The oil temperature is too high.

Probable causes

1. The machine is being operated above the intended capacity or in ambient temperatures that are too high for the design of the machine.

2. The viscosity of the oil is incorrect.

3. The setting of the pressure and flow compensator valve is too low. This low setting causes the pressure and flow compensator valve to remain open.

4. The pump has too much wear.

5. There is a restriction in an oil passage.

6. There is a leak in one or more circuits.

7. The oil level is low.

8. The oil is contaminated.

9. The hydraulic oil temperature sensor is faulty.

10. The pump is not destroking.

Problem 2

There is a pause before pressure is reached in all circuits. All implement functions are sluggish.

Probable causes

1. There is air in the signal network.

2. The oil level is too low.

3. The implement pump is worn or damaged.

4. The control valve is sticking.

5. There is a leak in the signal network or a resolver is malfunctioning.

6. The pilot oil pressure is inconsistent.

Problem 3

The grapple moves while the control lever is in the HOLD position.

Probable causes

1. The control valve and the valve spool have an excessive amount of wear.

2. A piston seal in a cylinder has an excessive amount of wear.

3. There is a leak in a connection between the control valve and the moving cylinders.

4. A check valve is not closing because of dirt or because of a worn seat.

5. The line relief valve or the makeup valve is open.

6. The control valve is not centering correctly. This problem can be caused by a broken spring or a sticky valve spool.

7. There may be residual pilot pressure in the system.

8. The pilot valve could be leaking.

9. The selector and pressure control valve could be leaking.

Problem 4

The grapple droops when the lift control lever is moved from the HOLD position to the UP position.

Probable causes

1. The oil is too cold.

2. There is air in the signal network.

3. The piston seals and/or the lift cylinders are worn.

4. Advanced signal passages in the main spool of the control valve are blocked in the affected circuit.

5. The load check valve is not closing. The return spring is weak or broken, or because there is dirt or debris in the check valve.

6. The spring on the compensator spool is broken in the control valve.

Problem 5

Line relief valves are noisy.

Probable causes

1. The affected relief valve is set too low.

2. The springs in the affected relief valve are fatigued or broken.

3. The pressure spool side of the pressure and flow compensator valve is set too high or the valve has failed.

Problem 6

Too much drift in the grapple.

Probable causes

1. The piston seals and/or the affected cylinders are worn.

2. The setting of the line relief valve is too low.

3. There is a leak past the line relief valve or the makeup valve for the affected circuit.

4. The spool in the main control valve is not centered correctly. The problem can be caused by a broken spring or a sticky valve spool.

5. If the drift is in the arch cylinders, the selector and pressure control valve may be leaking.

Problem 7

The cycle times for the arch, the boom, the tong, and the rotator are too slow.

Probable causes

1. The control valve for the main spool is not fully shifted for the affected circuit.

2. The load signal to the pressure and flow compensator valve is blocked or the signal is partially blocked. There is a leak in the signal network.

3. The line relief setting for the affected circuit is too low.

4. The line relief valve or the makeup valve for the affected circuit is leaking.

5. The piston seals and/or the affected cylinders are worn.

6. The pump is not at full stroke. The actuator piston is stuck or the swashplate is blocked.

7. The margin pressure setting is too low.

8. The selector and pressure control valve could be leaking.

9. There is leaking around the rotator motor.

10. The stroke limiters are not adjusted correctly.

Problem 8

The cycle times for the arch, the boom, the tong, and the rotator are too fast.

Probable causes

1. The margin pressure is set too high.

2. The engine high idle is set too high.

Problem 9

The grapple rotates too fast, or the grapple rotates too slowly.

Probable causes

1. The main spool for the control valve is not fully shifted for the affected circuit.

2. The stroke limiters are not adjusted correctly.

3. There is leaking around the rotator motor.