JLG M450 ANSI Service Manual - Manual (Page 119)

SECTION 4 - BOOM & PLATFORM
3121127 – JLG Lift – 4-7
4.6 MID AND LOWER LIFT CYLINDER
BLEEDING PROCEDURE
NOTE: Bleeding procedure should only be necessary if
rebuilding or replacing lift cylinder.
1. Check oil level in the hydraulic oil tank (all booms
must be retracted).
2. Lay an oil drip pan under the rod end port block
(Mid Cylinder) and crack bleeder open from the fit-
ting in the port block.
3. From the platform, turn the speed control knob to
the slow position.
4. Lift up very slowly. This will force any air out of the
circuit. If the lower boom is not extending, turn the
speed control up very slowly until the lower boom
starts to move.
5. Raise the lower boom approximately. 30.5 cm (1
foot), then close bleeder while the boom is still mov-
ing.
6. Lift down all the way.
7. Repeat this procedure until all air has been purged
from the circuit. Re-check the hydraulic oil level.
8. To test, cycle the lower lift function 3-4 times to see if
both cylinders stop at the same time when fully
extended.
4.7 WEAR PADS
1. Shim up wear pads until snug to adjacent surface.
2. Replace wear pads when worn to thickness shown
below.
3. Adjust wear pads as follows:
a. Loosen jam nut on adjustment bolt, turn bolt CW
until wear pad is snug to adjacent surface.
b. After adjustments have been made, tighten the
jam nuts on wear pad bolts.
Figure 4-6. Wear Pad Thickness
Table 4-1.Wear Pad Thickness
Pad
Thickness of
New Pad
Replace When Worn to:
A 0.75" 19 mm 0.375" 9.5 mm
B 0.5" 13 mm 0.3125" 8 mm
C 0.5" 13 mm 0.3125" 8 mm