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

Hydraulic System

Usage:

525D 2L5

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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.

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NOTICE

Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat products. Dispose of all fluids according to local regulations and mandates.

Problem 1

The pump makes unusual noise and the cylinder rods do not move evenly. There are also air bubbles in the oil.

Probable causes

The viscosity of the oil is incorrect.
The pressure and flow compensator valve opens at low oil pressure.
There is a loose connection of the oil line on the inlet side of the pump.
The pump has too much wear.
There is a leak in the oil line between the tank and the pump.
Pump cavitation.
The pressure and flow compensator valve opens and the pressure and flow compensator valve closes continuously.

Problem 2

The oil temperature is too high.

Probable causes

The machine is being operated above the intended capacity or in ambient temperatures that are too high for the specifications of the machine.
The viscosity of the oil is incorrect.
The setting of the pressure and flow compensator valve is too low. This condition causes the pressure and flow compensator valve to remain open.
The pump has too much wear.
There is a restriction in an oil passage.
There is a leak in one or more circuits.
The oil level is low.
The oil is contaminated.
There is air in the hydraulic oil.
Note: A problem with air in the hydraulic oil must be corrected before the hydraulic system will operate at normal temperatures. There are two conditions that cause air to be in the hydraulic oil:
- Return oil is flowing into the hydraulic oil tank above the level of oil that is in the tank.
- There are leaks in the oil suction line between the pump and the hydraulic oil tank.
The hydraulic oil temperature sensor is faulty.
The pump is not destroking.

Problem 3

The pump output is too low.

Probable causes

The oil level is low.
The viscosity of the oil is incorrect.
The implement pump has too much wear.
The margin pressure is set too low. The setting is too low in the pressure and flow compensator valve.
The spring on the flow spool is broken in the pressure and flow compensator valve.
The pump is not upstroking. The swashplate is blocked or the actuator spring is broken.
There is a leak in the signal network, or there is a malfunctioning resolver.

Problem 4

The oil pressure is low.

Probable causes

The relief valve for the priority flow control valve opens at low oil pressure.
The pump has too much wear.
An O-ring seal in the system failed.
The main control valve and the valve spool have an excessive amount of wear.

Problem 5

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

Probable causes

The control valve and the valve spool have an excessive amount of wear.
A piston seal in a cylinder has an excessive amount of wear.
There is a leak in a connection between the control valve and the moving cylinder or cylinders.
A check valve is not closing because of dirt, or because of a worn seat.
The line relief valve, or a makeup valve are open.
The control valve is not centering correctly. This problem can be caused by a broken spring or a sticky valve spool.
There may be residual pilot pressure in the system.

Problem 6

The decking blade or the grapple droops when the lift control lever is moved from the HOLD position to the RAISE position.

Probable causes

The oil is too cold.
There is air in the signal network.
The piston seals and/or the lift cylinders are worn.
Advanced signal passages in the main spool of the control valve are blocked in the affected circuit.
The load check valve is not closing. The return spring is weak or broken, or there is dirt or debris in the check valve.
The spring on the compensator spool is broken in the pressure and flow compensator valve.

Problem 7

The pump output is too high.

Probable causes

The pressure spool in the pressure and flow compensator valve is stuck.
The margin pressure is set too high. The setting is too high in the pressure and flow compensator valve. Check the pressure spool side of the pressure and flow compensator valve.
The pump is not destroking. The actuator piston is stuck or the swashplate is blocked.

Problem 8

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

Probable causes

There is air in the signal network.
The oil level is too low.
The implement pump is worn or damaged.
The control valve is sticking.
There is a leak in the signal network or a resolver is malfunctioning.
The pilot oil pressure is inconsistent.

Problem 9

The signal pressure is not zero when all the valves are in the HOLD position, and the steering is not active.

Probable causes

All controls are not in the HOLD position.
The signal network is not vented.
There is a leak into the signal resolver network.
The brake accumulator charging valve is not adjusted correctly.
The relief valve for the priority flow control valve is not adjusted correctly.

Problem 10

Too much drift in the decking blade or the grapple.

Probable causes

The piston seals and/or the affected cylinders are worn.
The setting of the line relief valve is too low.
There is a leak past the line relief valve or a makeup valve for the affected circuit.
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.
If the drift is in the arch cylinders, the pilot control valve may be leaking.

Problem 11

Line relief valves are too noisy.

Probable causes

The affected relief valve is set too low.
The springs in the affected relief valve are fatigued or broken.
The pressure spool side of the pressure and flow compensator valve is set too high or the valve has failed.

Problem 12

Hydraulic cycle times are too slow.

Probable causes

There is blockage in the signal network or there is leakage in the signal network.
The margin pressure setting is incorrect.
The pump is not at full stroke. The actuator piston is stuck or the swashplate is blocked.
The pump is malfunctioning.
There is excessive leakage from the pump output to the hydraulic oil tank.
The hydraulic oil filters are plugged.
The engine high idle setting is too low.

Problem 13

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

Probable causes

The main spool of the control valve is not fully shifted for the affected circuit.
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.
The line relief setting for the affected circuit is too low.
The line relief valve or a makeup valve for the affected circuit is leaking.
The piston seals and/or the affected cylinders are worn.
The pump is not at full stroke. The actuator piston is stuck or the swashplate is blocked.
The margin pressure setting is too low.
The pressure reducing valve could be leaking.
There is leaking around the rotator motor.
The stroke limiters are not adjusted correctly.

Problem 14

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

Probable causes

The margin pressure is set too high.
The engine high idle is set too high.

Problem 15

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

Probable causes

The main spool of the control valve is not fully shifted for the affected circuit.
The stroke limiters are not adjusted correctly.
There is leaking around the rotator motor.

Problem 16

The cycle times for the steering and decking blade are too slow.

Probable causes

The main spool of the control valve is not fully shifted for the affected circuit.
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.
The setting for the line relief valve for the affected circuit is too low.
The line relief valve for the affected circuit is leaking.
The piston seals and/or the affected cylinders are worn.
The flow control spring is broken.
The pump is not at full stroke. The actuator piston is stuck or the swashplate is blocked.
The margin pressure setting is too low.
The control linkage is not adjusted correctly.

Problem 17

The cycle times for the steering and decking blade are too fast .

Probable causes

The margin pressure is set too high.
The engine high idle is set too high.

Problem 18

The pressure for the signal resolver network is too high.

Probable causes

The brake accumulator charging valve is not adjusted correctly.
The relief valve for the priority flow control valve is not adjusted correctly.
The actuator piston is stuck or the swashplate is blocked.
The signal network is not vented.
All controls are not in the HOLD position.

Problem 19

The pressure in the signal resolver network is low.

Probable causes

The resolver is leaking or malfunctioning.
The actuator piston is stuck or the swashplate is blocked.

Problem 20

The steering wheel is difficult to turn.

Probable causes

The control valve spool is sticky.
The steering control linkage needs adjustment or the steering control linkage is binding.

Problem 21

The machine does not turn smoothly.

Probable causes

The differential lock is engaged.
The bearings in the articulation joint need lubrication or adjustment.
The oil level is low.

Problem 22

The machine turns too slowly in both directions.

Probable causes

Both of the relief valves are set too low.
Not enough flow from the pump.
The differential lock is engaged.
The pump pressure is too low.
The steering control linkage needs adjustment or the steering control linkage is binding.

Problem 23

The machine turns too slowly in one direction.

Probable causes

The steering control linkage needs adjustment or the steering control linkage is binding.
The control valve spool is not centered.
One relief valve is set too low.

Problem 24

The machine does not turn when the steering wheel is turned.

Probable causes