574B Forwarder Hydraulic System Machine Preparation for Troubleshooting Caterpillar

Machine Preparation for Troubleshooting

When you are analyzing a system for poor performance, remember that correct oil flow and correct oil pressure are necessary for correct operation. Oil flow increases with increased pump output. A restriction to the flow of oil increases the oil pressure.

For any test to a system, the hydraulic oil must be at the normal operating temperature. To increase the oil temperature, start the engine. Drive the machine for a short distance. Cycle the boom, the rotator, and the stick several times.

Before any tests are performed, visually inspect the complete system for oil leaks and for damaged parts. Also, visually inspect the wiring connectors and wiring harnesses for damage, corrosion, and contact.

Refer to the following warnings and notice for all inspections and tests of the machine.

------ WARNING! ------

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.


------ WARNING! ------

Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine.

To prevent possible injury, perform the procedure that follows before testing and adjusting the hydraulic system.



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, "AVSpare Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on AVSpare products.

Dispose of all fluids according to local regulations and mandates.

  1. Permit only one operator on the machine. Keep other personnel away from the machine.

    Illustration 1g00913180


  1. Park the machine on a smooth, level surface. Move away from other operating machines and away from personnel.

  1. Retract the extendable stick. Lower the grapple onto the bed.

    Illustration 2g00800981

    Operating Mode Switch on the Right Hand Control Unit

  1. Press the operating mode switch so that the machine is in the ROADING MODE position. The boom will not operate.

    Illustration 3g00811128

    Direction Selector Switch on the Left Hand Control Unit

  1. Place the direction selector switch in the NEUTRAL position.

    Illustration 4g00913302

    Parking Brake Switch

  1. Place the parking brake switch in the ON position. The ladder will lower.

    Illustration 5g00913309

    Steering Frame Lock (LOCKED Position)

  1. Install the steering frame lock with the two pins. Place blocks in front of the wheels and behind the wheels.

  1. Stop the engine by turning the engine start switch key to the OFF position. Turn the secondary disconnect switch and the battery disconnect switch to the OFF position.

  1. Make sure that all oil pressure is released in the system before you begin any work on the system.

When you troubleshoot the hydraulic system, ensure that the pressure settings are adjusted to the correct setting. Refer to Table 1 and Table 2 for the correct pressure settings.

Illustration 6g00937507

Table 1
Item     Function     Pressure Setting    
1     Maximum Signal Pressure    
21500 kPa (3100 psi)    
2     Parking Brake Release    
2800 kPa (400 psi)    
3     Gate (Vertical)    
4300 kPa (625 psi)    
4     Ladder    
2800 kPa (400 psi)    
5     Differential Lock    
2800 kPa (400 psi)    
6     Steering Signal Pressure    
18500 kPa (2685 psi)    
7     High Pressure Cutoff    
24000 kPa (3480 psi)    
8     Standby Pressure    
5000 kPa (725 psi)    

Table 2
Pressure Settings for the Implement Control Valve    
Item     Function     Solenoid     Port     Pressure Setting    
9     Extendable stick EXTEND     J     JJ    
10000 kPa (1450 psi)    
10     Extendable stick RETRACT     A     AA    
21500 kPa (3100 psi)    
11     Grapple CLOSE     K     KK    
21500 kPa (3100 psi)    
12     Grapple OPEN     B     BB    
12000 kPa (1750 psi)    
13     Grapple Rotate COUNTERCLOCKWISE     L     LL     N/A    
14     Grapple Rotate CLOCKWISE     C     CC     N/A    
15     Stick IN     M     MM     N/A    
16     Stick OUT     D     DD     N/A    
17     Boom UP     N     NN     N/A    
18     Boom DOWN     E     Plugged     N/A    
19     Swing LEFT     O     OO     N/A    
20     Swing RIGHT     F     FF     N/A    
21     Gate BACKWARD (1)
Boom TILT FORWARD (2)    
P     PP    
21000 kPa (3050 psi)    
22     Gate FORWARD (1)
Boom TILT BACKWARD (2)    
G     GG    
21000 kPa (3050 psi)    
23     Steering LEFT     Q     QQ    
17500 kPa (2550 psi)    
24     Steering RIGHT     H     HH    
17500 kPa (2550 psi)    
( 1 ) The hydraulically controlled gate (horizontal) is an optional attachment.
( 2 ) 574 booms

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