JLG M4069 Service Manual - Manual (Page 80)

SECTION 4 - HYDRAULICS
4-8 – JLG Lift – 3121824
WHEN INSTALLING NEW “POLY-PAK” TYPE PISTON SEALS,
ENSURE SEALS ARE INSTALLED PROPERLY. (SEE FIGURE 4-9.)
FOR CORRECT SEAL ORIENTATION. IMPROPER SEAL INSTALLA-
TION COULD RESULT IN CYLINDER LEAKAGE AND IMPROPER
CYLINDER OPERATION.
2. Using a soft mallet, tap a new wiper seal into the
applicable cylinder head gland groove. Install a new
wear ring into the applicable head gland groove.
3. Place a new o-ring and back-up seal in the applica-
ble outside diameter groove of the cylinder head.
4. Install a washer ring onto the rod, then carefully
install the head gland on the rod, ensuring that the
wiper and rod seals are not damaged or dislodged.
Push the head along the rod to the rod end, as
applicable.
5. Carefully slide the piston spacer onto the rod.
6. If applicable, correctly place a new o-ring and back-
up rings in the inner piston diameter groove.
7. Using suitable protection, clamp the cylinder rod in
a vise or similar holding fixture as close to the piston
as possible.
8. Carefully thread the piston on the cylinder rod hand
tight, ensuring that the o-ring and back-up rings are
not damaged or dislodged.
9. Thread the piston onto the rod until it abuts the
spacer end and install the tapered bushing.
NOTE: When installing the tapered bushing, the piston and
mating end of the rod must be free of oil.
WHEN REBUILDING THE LIFT CYLINDER, APPLY LOCTITE #242
T O TA P E R E D B U S H I N G B O LT S , T H E N T I G H T E N B O LT S
SECURELY. REFER TO TABLE 4-2, CYLINDER PISTON NUT
TORQUE SPECIFICATIONS AND TABLE 4-3, HOLDING VALVE
TORQUE SPECIFICATIONS FOR PROPER BOLT TORQUE VAL-
UES.
10. Install the bolts into the bushing using Loctite #242.
Refer to Cylinder Component Torque Specifications
Table for proper bolt torque values.
11. Remove the cylinder rod from the holding fixture.
12. Place new guidelock and hydrolock seals in the
applicable outside diameter grooves of both the pis-
ton and the cylinder head.
13. Position the cylinder barrel in a suitable holding fix-
ture.
EXTREME CARE SHOULD BE TAKEN WHEN INSTALLING THE
CYLINDER ROD, HEAD, AND PISTON. AVOID PULLING THE ROD
OFF-CENTER, WHICH COULD CAUSE DAMAGE TO THE PISTON
AND CYLINDER BARREL SURFACES.
Figure 4-6. Wiper Seal Installation
Figure 4-7. Installation of Head Seal Kit
Figure 4-8. Piston Seal Kit Installation