JLG G5-18A Service Manual - Manual (Page 108)

Hydraulic System
8-18 G5-18A, 2505H, 25.5
6. Inspect the hand brake valve and connections for
leaks, and check the level of the hydraulic fluid in the
reservoir. Shut the engine OFF.
7. Install the hand brake cover with the two capscrews.
8. Wipe up any hydraulic fluid spillage in, on, near and
around the machine, work area and tools.
9. Close and secure the battery and engine covers.
10. Remove the Do Not Operate Tags from both the
ignition key and the steering wheel.
d. Hand Brake Valve Test.
1. Start the machine and engage the shift lever to the
forward position. Slowly depress the throttle to mid
idle. The hand brake will not allow the machine to
move.
2. If further troubleshooting is required, refer to the
Section 8.7, “Hydraulic Schematic,” or Section 9.4,
“Electrical System Schematics.”
8.11.5 Steering Orbitrol Valve
Refer to Section 4.4.2, “Steering Column/Valve
Replacement,” for details.
8.11.6 Pilot Select Valve
The pilot select valve is attached to a manifold mounted
on a mounting plate inside the frame in front of the comp
cylinder.
Verify the correct operation of the pilot select valve
solenoids: boom lift/lower (3), auxiliary (4), tilt (5), boom
extend/retract (6) and front auxiliary (7) before
considering replacement of the valve. The housing of the
pilot select valve is not serviceable and must be replaced
if defective.
a. Pilot Select 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 battery and engine covers. Allow the
system fluids to cool.
4. Properly disconnect the battery.
5. Label or otherwise mark the hydraulic hoses in
relation to the pilot select valve. Disconnect and cap
all hoses, fittings, solenoid wire terminal leads, etc.
6. Remove the capscrews that attach the valve to the
frame.
7. Remove the pilot select valve from the machine.
Wipe up any hydraulic fluid spillage in, on, near and
around the machine.
b. Pilot Select Valve Disassembly, Cleaning,
Inspection and Assembly
1. Place the pilot select assembly on a suitable work
surface.
2. Remove the solenoid valves and cartridges (3, 4 &5)
from the steer select housing.
3. Clean all components with a suitable cleaner before
inspection.
4. 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.
5. 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 fluid 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.
6. Install the solenoid valves and cartridges in the pilot
select housing.
MU7720
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ANSI CE & AUS
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