JLG G6-42A Service Manual - Manual (Page 153)

8-19 G6-42A, G9-43A, G10-43A
Hydraulic System
Note: DO NOT disassemble the operating pump. The
pump is pre-set from the manufacturer. Any adjustments
or repairs performed by anyone other than an authorized
dealer could void the warranty.
b. Pump Installation
1. Place the pump and a new, oiled o-ring into position
on the transmission. Align the pump shaft with the
internal transmission gear, so that the machined
teeth mesh together.
2. Align the bolt holes with the pump mount holes.
3. Apply Loctite ® 242™ previously removed bolts
4. Secure the pump to the transmission with the
previously removed bolts and washers. Torque as
required.
5. Uncap and connect the previously labeled hydraulic
hoses to their appropriate locations.
6. Fill the hydraulic reservoir. Refer to Section 8.5.2,
“Hydraulic Oil Reservoir Filling.”
7. Prime the pump by filling the case drain port with fresh,
filtered hydraulic oil from a clean container before
installing the case drain connector and hose.
8. Check all routing of hoses and tubing for sharp
bends or interference with any rotating members. All
tube and hose clamps must be tight.
9. Properly connect the battery.
10. 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.
11. Inspect for leaks and check all fluid levels. The
hydraulic reservoir oil level must be to the middle of
the sight gauge.
12. Close and secure the engine cover.
13. Remove the Do Not Operate Tags from both the
ignition key switch and the steering wheel.
c. Pump Test
Refer to Section 8.3.1, “Pressure Checks and
Adjustments.”
8.7 CONTROL VALVES
8.7.1 Main Control Valve
The main control valve is mounted on the frame behind
the cab underneath a protective cover.
The main control valve assembly consists of four working
sections with their own valve assemblies, each providing
a specific hydraulic function.
Note: The optional main control valve for auxiliary
hydraulics contains a fifth valve section next to the
“frame level” section.
a. Main Control Valve Removal
1. Park the machine on a firm, level surface, level the
machine, 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.
3. Open the engine cover. Allow the system fluids to
cool.
4. Properly disconnect the battery.
5. Remove the main control valve protective cover.
6. Thoroughly clean the main control valve and
surrounding area, including all hoses and fittings,
before proceeding.
7. Drain the hydraulic fluid reservoir. Refer to Section
8.5.1, “Hydraulic Oil Reservoir Draining.”
8. Place a suitable container to catch hydraulic fluid
drainage beneath the frame.
Note: Slowly remove the hydraulic hoses attached to
the main control valve to relieve any possible trapped
pressure in the hydraulic line.
9. Label, disconnect and cap all the hydraulic hoses,
tubes and wires at the main control valve.
10. Wipe up any hydraulic fluid spillage in, on, near and
around the machine and the work area.
11. Remove the three bolts, washer and nuts (3)
securing the main control valve to the frame.