JLG 120HX Service Manual - Manual (Page 39)

SECTION 2 - PROCEDURES
3120819 – JLG Lift – 2-17
the bleeder port unplugged, venting all trapped air
to atmosphere. A suitable hose may be attached to
the bleeder port with the end in a container suitable
to contain the hydraulic fluid. After all air is vented
remove all attached hoses, and install the bleeder
port plug. Also plug the extend and retract ports until
cylinder is installed in boom.
2.12 BOOM MAINTENANCE
Removal
1. Shut down machine systems.
NOTE: Boom Assembly, less extend-a-reach and jib, weighs
approximately 4309 kg (9,500 lb.).
2. Using suitable lifting equipment, adequately support
boom weight along entire length of retracted boom.
HYDRAULIC LINES AND PORTS SHOULD BE CAPPED IMMEDI-
ATELY AFTER DISCONNECTING LINES TO AVOID ENTRY OF
CONTAMINANTS INTO SYSTEM.
3. Tag and disconnect hydraulic lines that run along
the side of the boom.
4. Remove hardware attaching upper lift cylinder
attach pin to boom.
5. Using a slide hammer or similar tool, and taking care
not to damage pin, remove pin from boom.
6. Using all applicable safety precautions, and only if
necessary, operate crane and fully retract lift cylin-
der.
7. Shut down machine systems.
8. Tag and disconnect all wiring to ground control box.
9. Remove boom length/angle indicator box.
10. Loosen and remove hardware securing boom pivot
pin.
11. Ensuring that boom is adequately supported and
using a suitable slide hammer, carefully remove
pivot pin from boom and turntable structure. Ensure
that boom and turntable structure are not damaged.
12. Carefully lift boom assembly clear of turntable and
lower to ground or suitably supported work surface.
Disassembly
NOTE: Left or right is determined facing the machine from
the platform.
1. Loosen the right side powertrack bracket and pow-
ertrack and lay on top of boom assembly.
HYDRAULIC LINES AND PORTS SHOULD BE CAPPED IMMEDI-
ATELY AFTER DISCONNECTING LINES TO AVOID ENTRY OF
CONTAMINANTS INTO SYSTEM.
2. Tag and disconnect hydraulic lines to slave level cyl-
inder and rotator motor.
3. Tag and disconnect wiring to platform control box.
4. Remove the left side powertrack.
5. Remove platform from boom assembly.
6. Remove cotter pins retaining telescope cylinder rod
attach pin to base section.
7. Using a suitable brass drift, carefully drive telescope
cylinder pin from base section.
8. Remove outer mid section extend chain adjust nut
and locknut at upper aft end of base section.
9. Remove bolts, washers and lockwashers attaching
outer mid section extend chain attach block to upper
aft end of base section. Remove block.
10. Remove fly section extend chain adjust nut and
locknut at lower front end of inner mid section.
11. Remove outer mid section retract chain adjust nut
and locknut at lower front end of base section.
12. Remove fly section retract chain adjust nut and lock-
nut at lower front end of inner mid section.
NOTE: Note and record the number and thickness of any
wear pad shims during wear pad removal.
13. Remove bolts and lockwashers attaching side wear
pads to front of base section. Remove pads and any
shims.
14. Remove bolts, washers and lockwashers attaching
lower front wear pads and mounting blocks to base
section. While supporting assembled fly, outer mid
and inner mid sections, remove wear pads, mount-
ing blocks and shims.
15. Remove bolts and lockwashers attaching top front
wear pad to base section. Remove pad and shims.
16. Using suitable lifting equipment, partially slide
assembled inner mid, outer mid and fly sections out
of base section.
17. Using suitable straps, tie off outer mid section retract
chains to underside of inner mid section as inner
mid, outer mid and fly sections are exiting base sec-
tion.