Operation and maintenance manual

Section 220-0140
Steering System - Emergency Valve
SM 1395 Rev 1 2-00
2
Emergency Steering
Numbers and letters in parentheses refer to Fig. 1.
Refer to Fig. 3 for hydraulic schematic of emergency
valve during emergency steering.
In the event of loss of pressure from the steering pump,
springs (5 & 6) return spool (3) to the left. The emergency
steering pump draws oil from the hydraulic tank and
pumps it to port 'B' of the emergency valve. The oil is
directed through the emergency valve and exits at port 'A'
to supply the steering system.
A pressure switch, installed in the block at the top port
on the main hydraulic pump, sends a signal to
illuminate the steering pressure warning light to indicate
a fault in the steering system supply pressure.
REMOVAL
WARNING
To prevent personal injury and property damage,
be sure wheel blocks are properly secured and of
adequate capacity to do the job safely.
1. Position the vehicle in a level work area, apply the
parking brake and switch off the engine. Turn steering
wheel in both directions several times to relieve any
pressure in the steering circuit.
2. Block all road wheels and place battery master
switch in the 'Off' position.
3. Clean outer area of the emergency valve with a
suitable solvent. Ensure all hydraulic lines connected
to the emergency valve are identified for ease of
installation and, with suitable containers available to
catch leakage, disconnect hydraulic lines. Fit blanking
caps to all open lines.
4. Remove mounting hardware securing emergency
valve assembly and remove emergency valve
assembly.
INSTALLATION
Note: Tighten all fasteners to standard torques listed in
Section 300-0080, STANDARD BOLT AND NUT
TORQUE SPECIFICATIONS.
SM - 544
4 - Emergency Valve
6 - Check Valve
1 - Hydraulic Tank
3 - Emergency Pump
Fig. 3 - Emergency Valve - Emergency Steering Operation
FLOW
AMPLIFIER
INLET
Note: Tighten all hydraulic lines fitted with ORFS
connections, as described in Section 220-0000,
STEERING SYSTEM SCHEMATIC. Renew all
'O' rings where used.
1. Install emergency valve assembly to the cradle
assembly at the rear of the cab and secure with
mounting hardware removed during removal.
2. Remove blanking caps and connect hydraulic lines
to the emergency valve as tagged at removal.
3. Check oil level in hydraulic tank and add oil as
required. Refer to Section 230-0040, HYDRAULIC
TANK, for correct fill level and Section 300-0020,
LUBRICATION SYSTEM, for oil specification.
4. Place the battery master switch in the 'On' position,
remove all wheel blocks and start the engine. Check all
lines and fittings for leaks and tighten as required.
MAINTENANCE
The emergency valve is a non-serviceable item except
in the instance of damage being caused to the seals.
Should a fault be diagnosed the cartridge assembly
can be unscrewed from the housing for inspection.
Check for sticking spool or faulty seals.
Refer to the vehicle's parts book for part numbers of
the cartridge kit and seal kit for the emergency valve.
* * * *