JLG G12-55A Service Manual - Manual (Page 134)

Hydraulic System
8-14 G10-55A, G12-55A
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 30 lb-ft (41 Nm).
e. 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 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 the tube and
hose clamps.
5. Fill the hydraulic fluid reservoir. Refer to Section
8.5.2, “Hydraulic Oil Reservoir Filling.”
6. Properly connect the batteries.
7. Start engine and run at approximately one-third to
one-half throttle for about one minute without moving
machine or operating any hydraulic functions.
8. 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.
9. Wipe up any hydraulic fluid spillage in, on, near and
around the machine, work area and tools.
10. Install the main control valve cover.
11. Close and secure the engine cover.
12. Remove the Do Not Operate Tags from both the
ignition key switch and the steering wheel.
f. Main Control Valve Test
Conduct a pressure check of the hydraulic system in its
entirety. Adjust pressure(s) as required. Refer to Section
8.3.1, “Pressure Checks and Adjustments.”
8.7.3 Service Brake Valve
a. Service Brake Valve Removal
1. Park machine on a firm, level surface, level machine,
fully retract boom, lower boom, place transmission
control lever in (N) NEUTRAL, engage park brake and
shut engine OFF.
2. Place a Do Not Operate Tag on both the ignition key
switch and steering wheel.
3. Open engine cover. Allow system fluids to cool.
4. Properly disconnect the batteries.
5. Label, disconnect and cap all hose attached to the
service brake valve.
6. Remove the service brake pedal. Refer to Section
4.3.2, “Service Brake Pedal.”
7. Remove the four capscrews, four nuts and four
lockwashers (3) mounting the service brake valve (4)
to the service brake bracket (5).
Note: DO NOT disassemble the service brake valve.
The service brake valve is not serviceable and must be
replaced in its entirety, if defective.
MAL0740
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