JLG 1850SJ Service Manual - Manual (Page 267)

SECTION 5 - BASIC HYDRAULIC INFORMATION & HYDRAULIC SCHEMATICS
3121619 – JLG Lift – 5-97
DISASSEMBLE CYLINDER BLOCK
1. Pull to remove slipper retainer (17) with pistons (16)
from cylinder (20).
NOTE: Units with high hourly usage may develop wear patterns.
Number pistons and bores for reassembly if reused.
2. Remove ball guide (18).
3. Remove three pins (19).
NOTE: Most repairs do not require block spring removal. Perform
this procedure on ly if you suspect problems w i th the block
spring.
RISK OF PERSONAL INJURY: COMPRESSING THE BLOCK
SPRING REQUIRES ABOUT 80 - 90 LBF (350 - 400 N). USE A
PRESS SUFFICIENT TO MAINTAIN THIS FORCE WITH REA-
SONABLE EFFORT. ENSURE SPRING IS SECURE BEFORE
ATTEMPTING TO REMOVE THE SPIRAL RETAINING RING.
RELEASE PRESSURE SLOWLY AFTER RETAINING RING IS
REMOVED.
4. Turn block over. Using a press, apply pressure on block
spring washer (23) to compress block spring (22).
Remove retaining ring (24). Carefully release pressure
and remove outer block spring washer (23), block spring
(22), and inner block spring washer (21) from cylinder
block.
Inspection
Wash all parts (including end-cap and housing) thoroughly
with clean solvent and allow to air dry. Blow out housing and
end cap oil passages with compressed air. Conduct inspection
in a clean area and keep all parts free from contamination.
Clean and dry parts again after any rework or resurfacing.
PISTONS AND SLIPP E R S
1. Inspect pistons for damage and discoloration. Discol-
ored pistons may indicate excessive heat; do not reuse.
2. Inspect running surface of slippers. Replace piston
assemblies with scored or excessively rounded slipper
edges. Measure slipper foot thickness. Replace exces-
sively worn slippers. Check slipper axial end-play.
Replace piston assemblies with excessive end-play.
BALL GUIDE, SLIPPER RETAINER, AND HOLD DOWN
PINS
1. Ball guide should be free of nicks and scratches, and not
excessively scored. Examine for discoloration that may
indicate excessive heat or lack of lubrication.
2. Slipper retainer should be flat. Slippers should fit in
retainer with minimal side play. Place hold-down pins
on a flat surface and roll them to make sure they are
straight. Replace any damaged parts.
BLOCK SPRING, AND WASHERS
Cylinder block, spring, and washers should show minimum
wear. Replace if cracks or other damage is present.
16
17
18
19
20
21
22
23
24
Figure 5-126. Cylinder Block Disassembly
Slipper
Maximum End Play
0.002 in (0.05 mm)
Minimum Slipper
Foot Thickness
0.127 in (3.23 mm)
Figure 5-127. Piston and Slipper Wear Measurement