JLG G6-42A Service Manual - Manual (Page 147)

8-19 G6-42A, G9-43A, G10-43A
Hydraulic System
1. To disassemble the individual sections of the main
control valve, remove the nuts from one end of the
tie rods (4). Pull the tie rods out through the sections.
2. Disassemble each section assembly as required.
Some sections include a pre-adjusted relief valve that
regulates pressure in a specific circuit.
Note: DO NOT adjust any of the relief valve assemblies!
Tampering with a relief valve will irrevocably alter
pressure in affected circuit, requiring recalibration or
a new relief valve.
Disassemble each Valve Section
1. Carefully separate the load sense outlet section from
lift/lower section.
2. Remove o-rings from between two sections.
3. Carefully separate each remaining sections, being
careful not to lose the load sense shuttle ball.
4. Remove both end caps from each end of the valve
sections then remove each control spool.
5. Remove any check valves, compensator valves,
anti-cavitation valves or shock valves from individual
valve section if equipped.
6. Keep all parts being removed from individual valve
sections tagged and kept together.
c. Main Control Valve Parts Cleaning
Clean all components with a suitable cleaner, such as
triclorethylene, before continuing. Blow dry.
d. Main Control Valve Parts Inspection
Inspect all parts and internal passageways for wear,
damage, etc. If inner surfaces of any component DO NOT
display an ultra-smooth, polished finish, or are damaged
in any way, replace the damaged part. Often, dirty
hydraulic fluid causes failure of internal seals, damage to
the polished surfaces within the component, and wear of
and/or harm to other parts.
e. Main Control Valve Assembly
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.
Assemble each Valve Section
1. Reassemble any check valves, compensator valves,
anti-cavitation valves or shock valves from each
individual valve sections if equipped.
2. Install the control spool being careful not to nick or
scratch the valve section bore or the control spool.
3. Install the end caps on each end of the valve section.
Assemble the Main Control Valve.
1. Place all three tie rods with the washers and nuts
through the end main control valve section.
2. Stand the end main control valve section on end.
3. Install the proper o-rings and load sense shuttle on
the inner face of the end main control valve section.
Align the next valve section over the three tie rods
and slide onto the end main control valve section.
4. Using the proper o-rings and load sense shuttle,
repeat step three for the remaining valve sections
and lastly the inlet end valve section.
5. Install the three washers and nuts on the tie rods.
Torque to 32 lb-ft (43 Nm) for the G6-42A and to
42 lb-ft (57 Nm) for the G9-43A and G10-43A.
f. Main Control Valve Installation
1. Install the main control valve onto the frame, aligning
the bolts with the holes in the end sections of the
main control valve. Slide the main control valve into
position, and tighten the bolts.
2. Prime the main control valve by filling the inlet
openings with fresh, filtered hydraulic oil from a
clean container, before attaching the hoses.
3. Use new oiled o-rings as required. Uncap and
connect all previously labeled hoses, clamps, etc. to
the main control valve.
4. 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.
5. Fill the hydraulic fluid reservoir. Refer to Section
8.5.2, “Hydraulic Oil Reservoir Filling.”
6. Start the engine and run at approximately one-third
to one-half throttle for about one minute without
moving the machine or operating any hydraulic
functions.
7. 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.
8. Wipe up any hydraulic fluid spillage in, on, near and
around the machine, work area and tools.
9. Install the main control valve protective cover.