JLG G12-55A AccuPlace Service Manual - Manual (Page 111)

8.21 G10-55A & G12-55A AccuPlace
Hydraulic System
3. Open the engine cover. Allow the system fluids to
cool.
4. Disconnect the battery negative (-) cable from the
battery negative (-) terminal.
5. Label, disconnect and cap the hydraulic hoses and
the electrical plugs connected to the steering select
valve.
6. Remove the bolts holding the steer select valve to
the mounting plate on the frame.
7. Remove the steer select manifold with the attached
steer select valve from the machine. Wipe up any
hydraulic fluid spillage in, on, near and around the
machine.
b. Steer Select Manifold and Valve 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 four socket head capscrews. Discard
the four o-rings.
3. Remove the solenoid valves and cartridges 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 fluid causes
failure of internal seals and damage to the polished
surfaces within the secondary function manifold.
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
four new, oiled o-rings and the four socket head
capscrews.
c. Steer Select Valve and Manifold Installation
1. Install the steer select valve to the mounting plate on
the underside of the frame near the transmission
using the two bolts.
2. Connect all the hydraulic hoses, fittings, solenoid
wire terminal leads, etc., to the steer select 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 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 cover.
d. Steering Test
Refer to Section 8.4.1, “Hydraulic Pressures.”
1. Conduct a pressure check of the steering hydraulic
circuit.
2. Check each steering mode for proper function.