JLG 2658E3 Service Manual - Manual (Page 24)

SECTION 2 - PROCEDURES
2-12 – JLG Lift – 3120878
ferential direction are acceptable provided they can-
not cut the rod seal. Chrome should be present over
the entire surface of the rod; the lack of chrome on
the rod surface is unacceptable. If an unacceptable
condition exists, repair or replace the rod.
3. Inspect the threaded portion of the rod for excessive
damage. Dress the threads as necessary.
4. Inspect inner surface of cylinder barrel tube 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 12.7 mm
(0.5 inch) long and primarily in the circumferential
direction are acceptable provided they cannot cut
the piston seal.
5. Inspect the threaded portion of the barrel tube for
damage. Dress the threads as necessary.
6. Inspect piston outside surface for scratches or pol-
ishing. Deep scratches are unacceptable. Polishing
indicates uneven loading and when this occurs, the
diameter should be checked for out-of-roundness. If
out-of-roundness exceeds 0.178 mm (0.007 inch),
this is unacceptable. Check the condition of the seal
and o-ring, looking particularly for metallic particles
embedded in the seal and o-ring surfaces. Remove
the seal and o-ring. Damage to the seal grooves,
particularly on the sealing surfaces, is unacceptable.
If an unacceptable condition exists, replace the pis-
ton.
7. Inspect the piston spacer for burrs and sharp edges.
If necessary, dress inside diameter surface with
Scotch Brite or equivalent.
8. Inspect the cylinder head inside bore for scratches
or polishing. Deep scratches are unacceptable. Pol-
ishing indicates uneven loading and when this
occurs, the bore should be checked for out-of-
roundness. If out-of-roundness exceeds 0.178 mm
(0.007 inch), this is unacceptable. Check for the
condition of the dynamic seals, looking particularly
for metallic particles embedded in the seal surface. It
is normal to cut the static seal on the retaining ring
groove upon disassembly. Remove the rod seal,
static o-ring, backup ring, and rod wiper. Damage to
the seal grooves, particularly on the sealing sur-
faces, is unacceptable. If an unacceptable condition
exists, replace the head.
9. Inspect the port block fittings and holding valve.
Replace as necessary.
10. Inspect the oil ports for blockage or the presence of
dirt or other foreign material. Repair as necessary.
Assembly
NOTE: Prior to cylinder assembly, ensure that the proper
cylinder seal kit is used. Refer to the Illustrated Parts
Manual.
NOTE: Apply a light film of hydraulic oil to all components
prior to assembly.
WHEN INSTALLING NEW “POLY-PAK” TYPE PISTON SEALS,
ENSURE SEALS ARE INSTALLED PROPERLY. REFER TO FIGURE
2-7 FOR CORRECT SEAL ORIENTATION. IMPROPER SEAL
INSTALLATION COULD RESULT IN CYLINDER LEAKAGE AND
IMPROPER CYLINDER OPERATION.
1. Using round-nose pliers or special installation tools,
twist the loaded u-cup seal into a “C” shape and
allow it to snap into the groove. Use a similar tech-
nique for installing the wiper.
2. Install a new static o-ring and back-up o-ring into the
static seal groove, verifying that the back-up o-ring is
closest to the threads. Install a new sealing o-ring
into the groove between the threads and the flange
lip. Install a new wear ring into the inside applicable
head groove. If possible, the head/seal assembly
should sit for at least one hour to allow the seals to
elastically restore.
3. Carefully slide the head assembly onto the cylinder
rod, ensuring that the wiper seal, o-ring and wear
ring are not damaged or dislodged.
4. Carefully slide the piston spacer on the rod. If appli-
cable, align the oil holes in the rod and the spacer.
Secure the spacer, if applicable.
5. Place a new o-ring in the inner piston diameter
groove.
6. Carefully place the piston on the cylinder rod, ensur-
ing that the o-ring is not damaged or dislodged.
7. Using suitable protection, clamp the cylinder rod in
a vise or similar holding fixture as close to the piston
as possible.
8. Push the piston onto the rod until it abuts the spacer
end and install the attaching nut.
APPLY “LOCQUIC PRIMER T” AND LOCTITE #242 TO PISTON
NUT THREADS, THEN TIGHTEN NUT TO TORQUE SHOWN IN
TABLE 2-1.
9. Torque the piston nut to the proper torque as out-
lined in the Figure 2-1, Cylinder Component Torque
Specifications