JLG 450A_AJ Series II Service Manual - Manual (Page 257)

SECTION 5 - HYDRAULICS
3121290 – JLG Lift – 5-17
IMPROPER SEAL INSTALLATION CAN CAUSE CYLINDER LEAKS AND IMPROPER
CYLINDER OPERATION. ENSURE ‘POLY-PAK’ PISTON SEALS ARE PROPERLY
INSTALLED. REFER TO WIPER SEAL INSTALLATION FOR CORRECT SEAL ORIEN-
TATION.
2. Place new wiper in cylinder head with flat side facing in.
Use a soft mallet to seat wiper in cylinder head groove.
3. Install retainer in cylinder head groove.
4. Install O-ring in cylinder head groove.
5. Place new O-rings and back-up ring in outside diameter
cylinder head grooves.
Figure 5-29. Installation of Head Seal Kit
6. Carefully install head on rod, ensuring wiper and rod
seals are not damaged or dislodged. Push head along
rod to rod end, as applicable.
7. 450A only. Carefully slide piston spacer on rod.
NOTE: Upper telescope cylinder piston has an O-ring installed
inside spacer.
8. Place new O-ring and in inner piston diameter groove.
9. Using suitable protection, clamp cylinder rod in a vise or
similar holding fixture as close to piston as possible.
10. Carefully thread piston on cylinder rod. Do not damage
or dislodge O-ring. Torque to 295 ft-lb (400 Nm).
11. Install retaining ring on end of rod.
12. Install seal and wear rings in outside piston grooves.
Figure 5-30. Piston Seal Installation
13. Remove cylinder rod from holding fixture.
14. Position cylinder barrel in suitable holding fixture.
INSERTING ROD OFF-CENTER CAN DAMAGE PISTON AND CYLINDER BARREL SURFACES.
USE EXTREME CARE WHEN INSTALLING CYLINDER ROD, HEAD, AND PISTON.
15. Clamp barrel securely and support rod. Insert piston end
into barrel cylinder. Do not damage or dislodge piston
O-rings and backup ring.
16. Continue pushing rod into barrel. Screw in cylinder
head. Torque to 442 ft-lb (600 Nm).
Figure 5-31. Cylinder Head Installation
NOTE: Marks made during disassembly should line up.