JLG G5-18A Service Manual - Manual (Page 93)

8.19 G5-18A/2505
Hydraulic System
3. Open the engine covers. Allow the system fluids to
cool.
4. Label or otherwise mark the hydraulic hoses in
relation to the inching valve. Disconnect and cap all
hoses, fittings, solenoid wire terminal leads, etc.
5. Remove the capscrews that attach the valve to the
frame.
6. Remove the inching valve from the machine. Wipe
up any hydraulic fluid spillage in, on, near and
around the machine.
b. Inching Valve Disassembly, Cleaning, Inspection
and Assembly
1. Place the inching valve assembly on a suitable work
surface.
2. Remove the solenoid valve and cartridge from the
inching valve housing.
3. Clean all components with a suitable cleaner before
inspection.
4. Inspect the solenoid cartridge 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 inching 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 valve and cartridge in the inching
valve housing.
c. Inching Valve Installation
1. Attach the inching valve to the mounting plate on the
frame using the socket head capscrews.
2. Connect the hydraulic hoses, fittings, solenoid wire
terminal leads, etc., to the inching valve.
3. Check the routing of all hoses, wiring and tubing for
sharp bends or interference with any rotating
members, and install tie wraps and/or protective
conduit as required. Tighten all tube and hose clamps.
4. Start the engine and run at approximately 1/3-1/2
throttle for about one minute, without moving the
machine or operating any hydraulic functions.
5. Inspect for leaks and check the level of the hydraulic
fluid in the reservoir. Shut the engine OFF.
Note: Check for leaks and repair as required before
continuing. Add hydraulic fluid to the reservoir as needed.
6. Wipe up any hydraulic fluid spillage in, on, near and
around the machine, work area and tools.
7. Close and secure the engine covers.
d. Inching Test
1. Conduct a pressure check of the inching hydraulic
circuit. Refer to Section 8.5, “Hydraulic Pressure
Diagnosis.”
2. Check inching brake for proper function.
8.10.8 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 an 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.
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