797F Off-Highway Truck Steering System: Troubleshooting PART 2

Problem: The machine turns too slowly in both directions

Probable Cause

• Not enough oil flow from the steering piston pump
• Malfunction of steering check and relief valves
• Failed steering accumulator
• The priority spool, the amplifier piston, or the directional spool will only allow partial flow.

Problem: Machine turns too slowly in one direction

Probable Cause

• The directional spool does not shift fully due to restriction at one end.
• Restriction in steering metering pump
• Malfunction of the steering check and relief valves

Problem: The steering wheel does not return to the center position correctly

Probable Cause

• Tight cover on steering metering pump
• Interference of components on steering column with shaft
• Restriction between spool and sleeve in the steering metering pump
• Damaged centering springs in steering metering pump
• Broken centering springs in steering metering pump

Problem: Hot oil temperature

Probable Cause

• The steering piston pump does not go to standby pressure.
• Wrong oil viscosity
• Air in the oil
• Pressure setting of the steering relief valve is too low.
• Restriction in the line circuit
• Leaking oil by the steering solenoid

Problem: Low oil pressure

Probable Cause

• Low pressure setting of the flow compensator valve in the pressure and flow compensator valve
• Worn steering piston pump
• Bad steering solenoid for the steering accumulators
• Malfunction of accumulator pressure sensor

Problem: Steering wheel turns with no operator effort

Probable Cause

• The sleeve in the steering metering pump sticks due to foreign material.
• The spool in the steering metering pump sticks due to foreign material.
• Broken centering springs in the steering metering pump
• Damaged centering springs in the steering metering pump

Problem: Soft steering

Probable Cause

• Air in the steering hydraulic circuit
• Low oil level in the steering hydraulic tank
• The steering accumulator has failed, and the steering accumulator has released nitrogen into the hydraulic system.

Problem: The steering piston pump does not destroke to standby pressure

Probable Cause

• The timing between the gerotor and pin (1) on the steering metering pump is not correct.

Timing of the steering metering pump (1) Pin (2) Drive (3) Timing mark (4) Valley of the gerotor star (A) Reference line (B) Reference line(C) Reference line

Timing mark (3) on drive (2) must fall on the parallel line between any two valleys of the gerotor star (4) .

Note: Reference line (A), reference line (B) and reference line (C) are parallel.

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