JLG 19BD Service Manual - Manual (Page 37)

SECTION 2 - SERVICE PROCEDURES
3121154 – JLG Lift – 2-15
2.8 HYDRAULIC LIFT CYLINDER - REMOVAL,
INSPECTION AND REBUILD
HYDRAULIC CYLINDERS ARE DESIGNED TO HOLD HYDRAULIC
FLUID UNDER HIGH PRESSURE. BE SURE ALL APPROPRIATE
MEASURES ARE TAKEN TO RELIEVE RESIDUAL PRESSURE IN
THE CYLINDER BEFORE DISCONNECTING LINES.
Removal of the hydraulic cylinder from the mast assembly
requires the removal of the mast assembly from the base
frame. The mast assembly can then be supported on it’s
back and partially disassembled to remove the hydraulic
cylinder.
Mast Removal
NOTE: This procedure depends on enough clearance over
the top of the mast to lift the mast assembly out of
the base frame. Otherwise the base frame assembly
will need to be unbolted from the work surface.
1. Disconnect power source from the AC Junction Box.
2. Remove the platform assembly from the front of the
mast assembly.
NOTE: The following step is done to prevent leakage of the
hydraulic fluid through the vented reservoir cap while
the mast is laid on it’s back for disassembly.
3. Remove the vented hydraulic reservoir cap and seal
the opening by layering plastic wrap over the cap
opening and screwing the cap back on tight.
4. Loosen the bottom fasteners of the mast side sup-
port rails, then remove the top fasteners attaching
the supports to mast support bracket which is
attached midway up the back of the mast. Rotate the
side support brackets down out of the way.
5. Place a sling capable of lifting the weight of the mast
assembly around and under the sides of the AC box/
Ground Station support beam bolted to the back of
the mast. With the sling attached to the lifting device
at the front of the mast.
6. Attach sling to an overhead crane or suitable fork lift
and lift sling to remove any slack in the lifting sling.
NOTE: It is important not to allow the mast assembly to
move around too much once the mast mounting fas-
teners are removed in the next step. To prevent the
manual descent valve assembly located on the bot-
tom of the mast from getting damaged.
7. Remove the four (4) mast mounting bolts, nuts and
washers attaching the mast to the base frame at the
back and bottom of the mast assembly. Lift mast
slightly if required to remove the bolts.
8. Push the mast assembly forward to allow the man-
ual descent valve to clear the circular opening in the
back of the base frame, before lifting the mast
assembly upwards.
9. Once the mast assembly is clear of the frame, move
it to an area large enough to allow disassembly.
When placing mast assembly on it’s back, place
supports under the mast, do not allow the mast to
rest on either the Ground Control or AC Junction
Box, or the manual descent valve assembly at the
bottom of the mast.