450E Backhoe Loader Machine Electronic Control System Steering System Caterpillar

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When performing this adjustment, put the hydraulic controls lockout lever in the LOCKED position and stop the engine.

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Sudden movement of the machine or release of oil under pressure can cause serious injury to persons on or near the machine. To prevent possible injury, perform the procedure that follows before testing and adjusting the hydraulic system.

Problem List for Two-Wheel Steering

1. Too much force is required to turn the steering wheel.

2. The machine turns too slowly in both directions.

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

4. The steering wheel turns with no assistance from the operator.

5. The steering oil pressure is too high.

6. The steering oil pressure is too low.

Problem 1

Too much force is required to turn the steering wheel on a two steering wheel machine.

Probable Causes

1. The signal pressure limiting valve is set too low.

2. There is a leak in the final resolver in the inlet manifold.

3. The priority spool is stuck.

4. The standby pressure is set too low.

5. The pump oil pressure is low.

6. The steering control unit covers are too tight.

7. The steering control unit is faulty.

8. The steering cylinder has failed.

9. There are mechanical problems in the axle.

10. The dynamic purge orifice in the priority valve is blocked.

Problem 2

The machine turns too slowly in both directions.

Probable Cause

1. There is not enough oil flow from the hydraulic pump. Check the pump control and the case drain for leakage.

2. The operation of the inlet section and the priority valve are not correct.

3. The seals for the steering cylinder are leaking.

4. The resolver has a leak.

5. The margin pressure is set too low.

6. The makeup valve is open.

Problem 3

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

Probable Cause

1. The priority valve is stuck.

2. The steering cylinder has worn parts.

3. There is a restriction in the steering linkage.

4. There is air in the system.

5. The metering pump is not operating properly.

6. There is dirt in the system.

7. The oil in the hydraulic tank is low.

Problem 4

The steering wheel turns with no assistance from the operator.

Probable Cause

1. There is foreign material in the metering pump, which causes the sleeve valves to stick.

2. The centering springs for the metering pump are broken or damaged.

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Illustration 1	g00552777
(1) Pin. (2) Internal pump gear.

3. The timing of the drive for the metering pump is not correct. Pin (1) must align with the valley of the internal pump gear (2) .

Problem 5

The steering oil pressure is too high.

Probable Cause

1. The relief valve for steering is not adjusted to the specification.

Problem 6

The steering oil pressure is too low.

Probable Cause

1. The relief valve for steering is not adjusted to the specification.

2. There is a leak in the final resolver.

3. The crossover relief valve is set too low.