JLG 740AJ, Service And Maintenance Manual

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SECTION 5 - BASIC HYDRAULIC INFOR M ATION AND SCHE M ATICS
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2. Use a soft mallet to tap a new wiper seal into the appli-
cable cylinder head gland groove. Install a new wear
ring into the applicable cylinder head gland groove.
3. Place a new o-ring and backup ring in the applicable
outside diameter groove of the cylinder head.
4. Install washer ring onto rod, carefully install the head
gland onto the rod, ensuring that the wiper and rod seal
are not damaged or dislodged. Push the head along the
rod to the rod end, as applicable.
5. Using suitable protection, clamp the cylinder rod in a
vise or similar holding fixture as close to piston as possi-
ble.
6. Carefully thread the piston on the cylinder rod and hand
tight, ensuring that the o-ring and backup rings are not
damaged or dislodged.
7. Remove the cylinder rod from the holding fixture.
8. Place a new o-ring in the inner piston diameter groove.
9. Place new seals in the outer piston diameter groove. (A
tube, with I.D. slightly larger than the O.D. of the piston
is recommended to install the solid seal.)
10. Position the cylinder barrel in a suitable holding fixture.
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.
11. With barrel clamped securely, and while adequately sup-
porting the rod, insert the piston end into the barrel cyl-
inder. Ensure that the piston loading hydrolock seals and
guidelock rings are not damaged or dislodged.
12. Secure Piston to the rod using nut.
13. Continue pushing the rod into the barrel until the cylin-
der head gland can be inserted into the barrel cylinder.
14. Secure the cylinder head gland using the spanner nut.
Torque to 275-300 ft.lbs (373- 407 Nm).
15. After the cylinder has been reassembled, the rod should
be pushed all the way in (fully retracted) prior to the
reinstallation of any holding valve or valves, if applica-
ble.
Figure 5-108. Wiper Seal Installation
CYLINDER
HEAD
RETAINER
RING
O-RING
BACKUP
RING
Figure 5-109. Installation of Head Seal Kit
Figure 5-110. Piston Seal Kit Installation
SPLIT SEAL
SEAL