120M, 12M, 140, 140M, 150, 14M, 160M, 160 and 16M Motor Graders Secondary Steering System Operational Checks Caterpillar

Operational tests of the steering system can be used in order to diagnose poor performance. Operational tests can also find the source of oil leakage inside the hydraulic system.

Note: Before you proceed with the operational checks of the secondary steering system make sure that the electrical system is functioning correctly. Refer to the electrical troubleshooting section.

When any test is performed on the steering system, the hydraulic oil must be at the normal operating temperature.

Problem: The Machine Does Not Turn When Activated

Probable Causes

• There is air in the steering system.

• The solenoid valves for the steering system are not functioning correctly.

• The crossover relief valve has failed.

Problem: There Is Excessive Drift In the Steering System

Probable Causes

• There is air in the steering system.

• The spool in the main control valve may not be centered.

• The spool in the main control valve is malfunctioning.

Problem: The Machine Turns Slowly In One Direction

Probable Causes

• The seals on the steering cylinder leak.

• The check valves leak in the steering control valve.

Problem: The Machine Turns Too Slowly

Probable Causes

• The springs for the flow control spool are not adjusted correctly.

• The steering pump is not producing enough flow.

• The seals on the steering cylinder leak.

• The check valve leaks in the steering control valve.

• The main relief valve is malfunctioning or the main relief valve pressure is set too low.

Problem: The Steering Pump Makes Noise but the Cylinder Rods Do Not Move Smoothly

Probable Causes

• The steering pump is leaking air into the system.

• The pump is worn.

• The viscosity of oil is wrong.

• The relief valve setting is wrong.

• The steering system is contaminated.

Problem: The Temperature of the Oil Is Too Hot

Probable causes

• The viscosity of the oil is wrong.

• The relief valve setting is too low.

• The pump is worn.

• There is a restriction in an oil passage.

• The seals on the steering cylinder leak.

Problem: The Steering Pump Output Is Low

Probable Causes

• There is a low oil level in the hydraulic tank.

• The viscosity of the oil is wrong.

• The pump is worn.

• There is a restriction on the inlet side of the steering pump.

• The steering pump is leaking air into the system.