JLG 723A Service Manual - Manual (Page 100)

Hydraulic System
8-18 L2906H, 2906H, 3507H, 619A, 723A, 29.6LP, 29.6, 35.7
8. Close and secure the engine cover.
9. Remove the Do Not Operate Tags from both the
ignition key switch and the steering wheel.
d. Parking Brake Valve Test.
1. Start the machine and engage the shift lever to the
forward position. Slowly depress the throttle to mid
idle. The parking brake will not allow the machine to
move.
2. If further troubleshooting is required, refer to the
Section 8.7, “Hydraulic Schematic,” or Section 9.9,
“Electrical System Schematics.”
8.11.5 Steering Orbitrol Valve
Refer to Section 4.4.2, “Steering Column/Valve
Replacement,” for details.
8.11.6 Steer Select Valve
The steer select valve is attached to inside the frame near
the front drive motor.
Verify the correct operation of the steer select valve
solenoids before considering replacement of the valve.
The housing of the steer select valve is not serviceable
and must be replaced if defective.
a. Steer Select Manifold and Valve Removal
1. Park the machine on a firm, level surface, fully
retract the boom, lower the boom, place the
transmission control lever in (N) NEUTRAL, engage
the park brake and shut the engine OFF.
2. Place a Do Not Operate Tag on both the ignition key
switch and the steering wheel, stating that the
machine should not be operated.
3. Open the engine cover. Allow the system fluids to
cool.
4. Label or otherwise mark the hydraulic hoses in
relation to the steer select manifold. Disconnect and
cap all hoses, fittings, solenoid wire terminal leads,
etc.
5. Remove the capscrews that attach the manifold to
the frame.
6. Remove the steer select manifold with attached steer
select valve from the machine. Wipe up any
hydraulic oil spillage in, on, near and around the
machine.
b. Steer Select Valve and Manifold Disassembly,
Cleaning, Inspection and Assembly
1. Place the steer select assembly on a suitable work
surface.
2. Separate the steer select valve from the manifold by
removing the capscrews. Discard the old o-rings.
3. Remove the solenoid valves and cartridges (1) from
the steer select housing.
4. Clean all components with a suitable cleaner before
inspection.
5. Inspect the solenoid cartridges for proper operation.
Check by shifting the spool to ensure that it is
functioning properly. Check that the spring is intact.
Inspect the cartridge interior for contamination.
6. Inspect internal passageways of the steer select
manifold and valve for wear, damage, etc. If inner
surfaces of the manifold DO NOT display an ultra-
smooth, polished finish, or components are
damaged in any way, replace the manifold or
appropriate part. Often, dirty hydraulic oil causes
failure of internal seals and damage to the polished
surfaces within the unit.
Note: ALWAYS replace seals, o-rings, gaskets, etc.,
with new parts to help ensure proper sealing and
operation. Lubricate seals and o-rings with clean
hydraulic oil.
7. Install the solenoid valves and cartridges in the steer
select housing.
8. Attach the steer select valve to the manifold using
new, oiled o-rings and socket head capscrews.
c. Steer Select Manifold and Valve Installation
1. Attach the steer select manifold and valve to the
mounting plate on the frame using the socket head
capscrews.
MZ5540
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