- Perform a visual inspection. Refer to Testing and Adjusting, "Visual Inspection".
- If the problem has not been identified, do "Operation Checks".
- If the problem is still undetermined, do "Performance Checks".
- If the problem is still undetermined, do "Check The Warning System (Steering System)".
This procedure will help to identify the steering hydraulic system problems.
Operation Checks
The front wheels must be on a dry, smooth hard surface and the hydraulic oil in the steering system must be warm.
Start the machine. In first gear, slowly drive the machine while you turn the steering wheel. Drive the machine until the hydraulic oil temperature is approximately 38 °C (100 °F).
Test the steering system with the engine at high idle. Rotate the steering wheel. Measure the time that is required to turn the front wheels from the full right turn position to the full left turn position and back to the full right turn position. If the time is more than 6.0 seconds, there could be a problem in the steering hydraulic system. If the time is less than 5.0 seconds, there could be a problem in the steering hydraulic system.
Failures in the steering system can be at least one of the following items:
- Broken oil line or a leak in an oil line connection
- Worn steering piston pump
- Pressure setting of the flow compensator valve in the pressure and flow compensator valve
- Pressure setting of the high pressure cutoff valve in the pressure and flow compensator valve
- Low pressure setting of the primary steering relief valve
- Open secondary steering check valve
- Worn steering metering pump
- Leaking steering cylinder check and relief valves
- Worn steering cylinders
Performance Checks
Performance checks of the steering system can be used for the following purposes:
- Diagnosis of poor performance
- Source of oil leakage inside the hydraulic system
Problem : Noisy steering piston pump
Probable Cause
- Failed steering piston pump
- Air in the steering hydraulic circuit
- Loose connection of the oil line on the inlet side of the steering piston pump
- Loose connection of the oil line at the port on the steering hydraulic tank
- Low oil level in the steering hydraulic tank
- Wrong oil viscosity
Problem : Turning the steering wheel requires too much force
Probable Cause
Worn spool or sticking spool in the flow compensator valve
- Low oil in the steering hydraulic tank
- Worn steering piston pump
- Tight end cover on the steering metering pump
- Interference of components on steering column with shaft
- Overloaded steering axle
- Improper operation of steering metering pump
- Improper operation of the steering cylinder check and relief valves
- Kinked load sensing line
- Leaky load sensing line
- Turning the steering wheel faster than 70 rpm at low idle
- Turning the steering wheel faster than 242 rpm at high idle
- Thermal shock in the steering metering pump
Note: Thermal shock occurs when the temperature of the oil in the steering metering pump is 10 °C (50 °F) colder than the temperature of the oil in the steering hydraulic tank.
Problem : The truck does not turn when the steering wheel is turned
Probable Cause
- Air in system
- Malfunction of the steering cylinder check and relief valves
- Lack of oil in steering metering pump
- Worn steering metering pump
- Disengaged steering column shaft from steering metering pump
- Worn steering cylinders
Problem : Erratic steering
Probable Cause
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| Illustration 1 | g00533400 |
Timing of metering pump drive (1) Pin (2) Drive (3) Timing Mark (4) Gerotor star valleys (A) Reference Line (B) Reference Line (C) Reference Line | |
- Air in system
- Worn steering linkage
- Worn cylinder piston
- Loose cylinder piston
- Malfunction of the steering cylinder check and relief valves
- The timing of the gerotor and the timing of the pin (1) in the steering metering pump is not correct.
Problem : The truck turns too slowly in both directions
Probable Cause
- Not enough oil flow from the steering piston pump
- Low pressure setting of the flow compensator valve in the pressure and flow compensator valve
- Low pressure setting of the high pressure cutoff valve in the pressure and flow compensator valve
- Malfunction of the steering cylinder check and relief valves
Problem : The truck turns too slowly in one direction
Probable Cause
- Restriction in steering metering pump
- Malfunction of the steering cylinder 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 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
- Low pressure setting of the high pressure cutoff valve
- Low pressure setting of the primary steering relief valve
- Open secondary steering check valve
- Restriction in the line circuit
Problem : Low oil pressure
Probable Cause
- Worn steering piston pump
- Low pressure setting of the flow compensator valve
- Low pressure setting of the high pressure cutoff valve
- Low pressure setting of the primary steering relief valve
- Open secondary steering check valve
Problem : The steering wheel turns with little effort from the operator
Probable Cause
- The sleeve in the steering metering pump jams and the spool in the steering metering pump jams due to foreign material.
- Wrong oil line connections on the steering metering pump
- Broken centering springs in the steering metering pump
- Damaged centering springs in the steering metering pump
| | |
| Illustration 2 | g00533400 |
Timing of metering pump drive (1) Pin (2) Drive (3) Timing Mark (4) Gerotor star valleys (A) Reference Line (B) Reference Line (C) Reference Line | |
Problem : The steering piston pump does not destroke to standby pressure
Probable Cause
- Sticking spool in the flow compensator valve
- High pressure setting of the flow compensator valve
| | |
| Illustration 3 | g00533400 |
Timing of metering pump drive (1) Pin (2) Drive (3) Timing Mark (4) Gerotor star valleys (A) Reference Line (B) Reference Line (C) Reference Line | |
- Timing mark (3) that is on drive (2) must fall on the parallel line between any two gerotor star valleys (4) .
Note: Reference lines (A), (B) and (C) are parallel.
Problem : Soft steering
Probable Cause
- Air in the steering hydraulic circuit
- Low oil level in steering hydraulic tank
Check The Warning System (Steering System)
- Place blocks in front of the wheels and behind the wheels.
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| Illustration 4 | g01255384 |
Instrument cluster | |
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| Illustration 5 | g01254322 |
(1) Instrument cluster (2) Steering lock switch (3) Adviser system (4) Secondary steering and parking brake release switch (5) Secondary brake lever | |
- Place the gear selector in the neutral position.
Note: When the transmission gear selector in the P, friction will not allow the secondary steering system to turn the wheels all the way to the steering cylinder stops.
- Turn the engine start switch key to the ON position.
- The Caterpillar Monitoring System action light should flash and the action alarm should sound for approximately three seconds. Secondary steering indicator is activated and the electric motor for the secondary steering and brake electric drive pump must operate for three seconds.
- The secondary steering and brake, electric drive pump will operate when the secondary steering indicator light is ON. When the secondary steering system is used to steer the machine, more steering effort will be needed. The primary steering system will require less steering effort.
- Start the engine. Secondary steering warning indicator and the action alarm should turn off after three seconds.
- Operate the engine and move secondary steering and parking brake release switchl (4) to the MANUAL position. Secondary steering indicator should activate. The steering system must operate in the same way as normal steering operation. Secondary steering warning indicator, action light, and the action alarm should not activate.
- Move secondary steering and parking brake release switch (4) to the AUTO position and turn the engine start switch key to the OFF position.
- Put the transmission gear selector in P in oreder to apply the parking brakes.
Problem : The monitoring system, the lights, the action alarm, and the starter does not operate
Probable Cause
- The battery disconnect switch is in the OFF position.
- Low battery voltage
Problem : The secondary steering warning indicator, the action light, and the action alarm are activated after the engine starts with the secondary steering indicator and the electric motor is OFF.
Probable Cause
- The Power Train Electronic Control Module (Power Train ECM) is not receiving voltage from the "R" terminal on the alternator.
- Bad Cat Data Link
- Bad Power Train ECM
- Bad Caterpillar Monitoring System
Problem : The secondary steering warning indicator, the action light, the action alarm, the secondary steering indicator, and the electric motor are ON.
Probable Cause
- Bad steering pump oil pressure switch
- Low oil in the steering hydraulic tank
- Bad Power Train ECM
Problem : The secondary steering warning indicator and the action light flashes until the engine starts with the secondary steering indicator and the electric motor are OFF.
Probable Cause
- Open circuit or shorted circuit to ground on secondary steering relay that is mounted on the frame
- Open circuit or shorted circuit to ground on secondary steering relay that is mounted in the cab
- The contacts are corroded or the contacts have failed to open on the secondary steering relay that is mounted on the frame.
- Open circuit type failure from the positive "+" battery terminal to the secondary steering pump oil pressure switch terminal
- Open circuit type failure from the secondary steering relay that is mounted on the frame to the secondary steering and brake release electric drive pump
- Open circuit type failure from the electric motor to the negative terminal on the battery
- Failure of the electric motor
- The secondary steering and brake release electric drive pump will not turn.
- Bad Power Train ECM
Problem : The secondary steering warning indicator does not flash during engine start-up.
Probable Cause
- Bad Cat Data Link
- Bad Power Train ECM
- Bad Caterpillar Monitoring System
- Bad steering pump oil pressure switch
Problem : The secondary steering warning indicator and the action light flashes, but the secondary steering indicator and the electric motor operates after the engine starts.
Probable Cause
- Bad Power Train ECM
Problem : Secondary steering indicator does not turn ON and the electric motor does not operate when the secondary steering and brake control is placed in the Manual position.
Probable Cause
- Bad secondary steering and brake release control
- Open circuit between the secondary steering fuse and the secondary steering and brake control
- Open circuit between the secondary steering and brake release control and the secondary steering relay that is located behind the cab