JLG 19AMI (3120758) Service Manual - Manual (Page 34)

SECTION 2 - SERVICE PROCEDURES
2-20 – JLG Lift – 3120758
event that an unacceptable condition occurs, the head
should be replaced.
Piston
Visually inspect the outside surface for scratches or pol-
ishing. Deep scratches are unacceptable. Polishing indi-
cates uneven loading and when this occurs, the diameter
should be checked for out-of-roundness. If out-of-round-
ness exceeds 0.007", this is unacceptable. Check the con-
dition of the dynamic seals and bearings looking
particularly for metallic particles embedded in the bearing
and in the piston seal surface. Remove the seals and
bearings. Damage to the seal grooves, particularly on the
sealing surfaces, is unacceptable. In the event that an
unacceptable condition occurs, the piston should be
replaced.
Tube Assembly
Visually inspect the inside bore for scratches and pits.
There should be no scratches or pits deep enough to
catch the fingernail. Scratches that catch the fingernail but
are less than 0.5 inch long and primarily in the circumfer-
ential direction are acceptable provided they cannot cut
the piston seal. The roughness of the bore should be
between 10 and 20 µ inches RMS. Significant variation
(greater than 8 µ inches difference) are unacceptable. In
the event that an unacceptable condition occurs, the tube
assembly should be repaired or replaced.
Figure 2-2. Lift Cylinder Internal Component Assembly Cross-Section.
PISTON
LOCKNUT
(Torque
175-200 Ft. Lb.)
WEAR
RING
PISTON
SEAL
O-RING
O-RING
BACKUP
RING
CYLINDER
HEAD
RETAINING
RING
RETAINING RING
GROOVE
ROD
SEAL
ROD
WIPER
CYLINDER
HEAD
WHEN ASSEMBLING
CYLINDER
APPLY ANTI-SEIZE
COMPOUND
AROUND THE HEAD
IN THIS AREA ONLY
CYLINDER
TUBE
ASSEMBLY
CYLINDER
ROD