R2900G Load Haul Dump Steering System Caterpillar

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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 between the front and rear frames before working on the machine.

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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 by a doctor familiar with this type of injury. Always use a board or cardboard when checking for a leak.

Performance tests for the steering system can be used for a diagnosis of poor performance and for finding the source of oil leaks inside the hydraulic system.

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

Note: Make sure that the you use hydraulic oil with the correct viscosity for the ambient temperature and for the operating conditions. To determine the correct oil viscosity, see the reference that follows.

Reference: For additional information about the various lubricant viscosities, refer operation and maintenance manual, "lubricant viscosities" for the machine that is being serviced.

Note: The following information is for both STIC and wheel steering machines.

Problem 1: The machine turns slowly when the STIC steering control lever is moved or when steering wheel is turned.

Probable causes

• The oil is too cold.

• There is a restriction in the pilot lines of the pilot valve.

• The pilot lines to the pilot valve are not connected to the correct ports.

• Steering pump pressure low.

• Restriction in steering metering pump pilot lines (wheel steering).

• Pilot lines to steering metering pump are not connected to proper ports (wheel steering).

• Restriction across ball check valve at steering metering pump supply port in the steering control valve (wheel steering).

• Bolts are too tight for metering section of the steering pump (wheel steering).

Illustration 1	g01020354
Timing of the metering pump drive (1) Pin (2) Rotor

• Timing of the metering pump drive is not correct. Pin must align with the valley of the rotor.

Problem 2: The machine responds slowly when the machine is steered quickly away from a full turn.

Probable cause:

• The steering neutralizer valves do not move freely.

• Not enough clearance between ball check valve and plug assembly in steering neutralizer valve (wheel steering).

The STIC steering control lever or steering wheel attempts to turn the machine when the machine is in a full turn.

Probable causes:

• The adjustment of the steering neutralizer valve is not correct.

• Seal for the neutralizer ball check has a defect (wheel steering).

• The relief valve opens before the striker moves the neutralizer valve stem.

The machine does not turn smoothly.

Probable cause:

• The control valve spool does not move freely.

• Steering metering pump supply line has been installed in the field test port (in the steering valve body) instead of its correct location (wheel steering).

The machine turns too slow in both directions.

Probable causes:

• There is not enough flow from the steering pump.

• The control valve spool does not move all the way.

• Springs for the flow control valve are not adjusted correctly.

The machine turns too slow in one direction.

Probable causes:

• There is a faulty seal and/or seat in the shuttle valve (ball resolver).

• Flow balance adjustment of main control spool is not correct.

Reference: Refer to Testing and Adjusting, "Steering time check" for more information.

The machine turns correctly when moving, but is slow in both directions when the machine turns against a load (high resistance).

Probable causes:

• Oil is leaking past the relief valve seat or seals.

• The control valve spool does not fit correctly in the bore.

• Oil is leaking past both seats of the shuttle valve (ball resolver).

The machine turns correctly when moving, but the machine turns slowly in one direction when the machine turns against a load (high resistance).

Probable causes:

• Slow right turn: leakage past upper shuttle valve (ball resolver) seat or seals.

• Slow left turn: leakage past lower shuttle valve (ball resolver) seat or seals.

The machine does not turn when the steering control is moved.

Probable causes:

• The control valve spool will not move from the HOLD position.

• Oil is leaking past the relief valve seat or seals.

• A steering neutralizer valve stem does not return to the open position.

• Flow control valve will not move from the open position.

Note: Some steering "slip" is normal.

Reference: Refer to Testing and Adjusting, "Steering wheel slip - check" for more information.

The machine turns without moving the steering control.

Probable causes:

• The control valve spool will not return correctly to the HOLD position.

• The mounting bolts for the steering control valve are too tight.

• The bolts are too tight for the end covers of the steering control valve.

• Manufacturing tolerances for the control valve spool do not permit the spool to return to the HOLD position.

Note: This may be corrected by turning the spool in the steering control valve in its bore (turn end for end). To do this, the spring, retainer and shims must be installed on the opposite end of the spool. An adjustment may be necessary for the steering times.

The machine turns too fast so that small steering corrections can not be made at fast speeds.

Probable causes

• The steering control valve spool does not move freely.

• Metering orifices on the steering control valve spool are filled with foreign material or the orifices were not drilled correctly.

• The adjustment of the steering control valve spool is not correct.

Reference: Refer to Testing and Adjusting, "Steering time - check" for more information.

The pump makes noise and the steering cylinder pistons and cylinder rods do not move smoothly.

Probable causes:

• There is air in the steering hydraulic circuit.

• The pump has too much wear.

• There is a loose connection of the oil line on the inlet side of the pump.

• The viscosity of the oil is incorrect.

• The relief valve opens at low oil pressure.

• The tank oil level is low.

Steering wheel turns without operator turning it.

Probable causes

• Foreign material causes sleeve valves in hand metering unit to stick.

• Steering metering pump centering (leaf) springs are broken or damaged.

Steering wheel is hard to turn.

Probable causes:

• Oil is cold.

• Restriction in steering metering pump pilot lines.

• Pilot lines to steering metering pump are not connected to proper ports.

• Steering pump pressure is low.

• Bolts are too tight for metering section of the steering metering pump.

Steering wheel is hard to turn when steering quickly away from a full turn.

Probable cause:

• Not enough clearance between ball check and plug assembly in neutralizer valve.