Hydraulic Cylinders; General Cylinder Disassembly Instructions; General Cylinder Cleaning Instructions; General Cylinder Assembly Instructions - JLG sky trak mmv Service Manual

Hydraulic System
9.14

HYDRAULIC CYLINDERS

This section covers servicing the attachment tilt (1),
slave (2), extend/retract (3), lift/lower (4), frame sway (5),
stabilizer (6), steering (7) and fork side shift (8) cylinders
on the vehicle.
8
4
5
There are many factors involved with the proper disas-
sembly, cleaning, inspection, repair and reassembly of
hydraulic cylinders; therefore, only qualified profession-
als with proper training, supervision, tools and equipment
should rebuild the cylinders used on this vehicle.
For example, special pin spanner wrenches of the correct
size are needed to disassemble the cylinders. Also, the
lift/lower cylinder rod locknut must be torqued to
2200-2600 lb/ft (2034-3525 Nm); this requires a special
torque wrench and/or torque multiplier. If the proper
knowledge and equipment are not available, the cylinders
must be sent out for rebuilding by a competent profes-
sional at a company that specializes in rebuilding agricul-
tural and commercial heavy-equipment hydraulic cylinders.
Rebuild cylinders only in a clean, well-lighted area where
all components can be carefully and thoroughly inspect-
ed. If leaving a cylinder dismantled for any length of time
longer than the immediate rebuilding period, and especial-
ly in high-humidity environments, coat the metal parts with a
suitable preservative and place them in protective storage.
Refer to the specific instructions for removal, rebuilding
and installation of each cylinder.
9.142
3
1
2
7
Front
9.14.1 General Cylinder Disassembly
Instructions
WARNING:
burns, proceed with caution when applying heat to
parts.
IMPORTANT: Avoid the use of excessive heat, which
will damage parts and make them unusable.
Some cylinder parts are sealed with a special organic
sealant and locking compound. Before attempting to dis-
assemble these parts, remove any accessible seals from
the area of the bonded parts. Wipe off any hydraulic oil,
then heat the part(s) uniformly to break the bond. A tem-
perature of 300-400° F (149-204° C) will destroy the
bond. Avoid overheating, or the parts may become dis-
torted or damaged. Apply sufficient torque for removal
while the parts are still hot. The sealant often leaves a
6
white, powdery residue on threads and other parts, which
must be removed by brushing with a soft brass wire brush
prior to reassembly.
WARNING:
be trapped inside the cylinder. Exercise caution
when removing a counterbalance valve or a pilot-
operated check valve from a cylinder. Escaping
MM1851
hydraulic fluid under pressure can penetrate the
skin, causing death or serious injury.
DO NOT attempt to salvage cylinder seals, sealing rings
or o-rings. ALWAYS use a new, complete seal kit when
rebuilding hydraulic components. Consult the parts cata-
log for ordering information.
Note: An additional o-ring may be included at the base
of the cylinder rod. This additional o-ring may be discarded,
as it served only in a temporarily protective role.
9.14.2

General Cylinder Cleaning Instructions

Clean all reusable metal parts thoroughly after disassem-
bly and prior to inspection. Use an approved solvent such
as trichlorethylene.
9.14.3

General Cylinder Assembly Instructions

1. Before reassembly, ensure that parts are clean and
free from foreign matter. Use an approved solvent for
cleaning, such as trichlorethylene.
2. Use the proper tools for specific installation tasks.
Clean tools are required for installation.
3. Protect the finish on the rod at all times. Damage to
the rod can cause premature seal failure.
To help prevent severe
Significant pressure may
Model MMV Rev. 12/04