JLG 450AJ Service Manual - Manual (Page 19)

SECTION 2 - PROCEDURES
3120869 – JLG Lift – 2-3
3. Cloudy oils indicate a high moisture content which
permits organic growth, resulting in oxidation or cor-
rosion. If this condition occurs, the system must be
drained, flushed, and refilled with clean oil.
4. It is not advisable to mix oils of different brands or
types, as they may not contain the same required
additives or be of comparable viscosities. Good
grade mineral oils, with viscosities suited to the
ambient temperatures in which the machine is oper-
ating, are recommended for use.
NOTE: Metal particles may appear in the oil or filters of new
machines due to the wear-in of meshing compo-
nents.
Hydraulic Oil
1. Refer to Section 1 for recommendations for viscosity
ranges.
2. JLG recommends Mobilfluid 424 hydraulic oil, which
has an SAE viscosity of 10W-30 and a viscosity
index of 152.
NOTE: Start-up of hydraulic system with oil temperatures
below -26 degrees C (-15 degrees F) is not recom-
mended. If it is necessary to start the system in a
sub-zero environment, it will be necessary to heat
the oil with a low density, 100VAC heater to a mini-
mum temperature of -26 degrees C (-15 degrees F).
3. The only exception to the above is to drain and fill
the system with Mobil DTE 11 oil or its equivalent.
This will allow start up at temperatures down to -29
degrees C (-20 degrees F). However, use of this oil
will give poor performance at temperatures above49
degrees C (120 degrees F). Systems using DTE 11
oil should not be operated at temperatures above 94
degrees C (200 degrees F) under any condition.
Changing Hydraulic Oil
1. Use of any of the recommended crankcase or
hydraulic oils eliminates the need for changing the
oil on a regular basis. However, filter elements must
be changed after the first 50 hours of operation and
every 300 hours thereafter. If it is necessary to
change the oil, use only those oils meeting or
exceeding the specifications appearing in this man-
ual. If unable to obtain the same type of oil supplied
with the machine, consult local supplier for assis-
tance in selecting the proper equivalent. Avoid mix-
ing petroleum and synthetic base oils. JLG
Industries recommends changing the hydraulic oil
annually.
2. Use every precaution to keep the hydraulic oil clean.
If the oil must be poured from the original container
into another, be sure to clean all possible contami-
nants from the service container. Always clean the
mesh element of the filter and replace the cartridge
any time the system oil is changed.
3. While the unit is shut down, a good preventive main-
tenance measure is to make a thorough inspection
of all hydraulic components, lines, fittings, etc., as
well as a functional check of each system, before
placing the machine back in service.
Lubrication Specifications
Specified lubricants, as recommended by the component
manufacturers, are always the best choice, however,
multi-purpose greases usually have the qualities which
meet a variety of single purpose grease requirements.
Should any question arise, regarding the use of greases in
maintenance stock, consult your local supplier for evalua-
tion. Refer to Section 1 for an explanation of the lubricant
key designations appearing in the Lubrication Chart.
2.4 CYLINDERS - THEORY OF OPERATION
Systems Incorporating Double Acting
Cylinders
Cylinders are of the double acting type. Systems incorpo-
rating double acting cylinders are as follows: Slave Level,
Master Level, Lift, Telescope, Axle Lockout and Steer. A
double acting cylinder is one that requires oil flow to oper-
ate the cylinder rod in both directions. Directing oil (by
actuating the corresponding control valve to the piston
side of the cylinder) forces the piston to travel toward the
rod end of the barrel, extending the cylinder rod (piston
attached to rod). When the oil flow is stopped, movement
of rod will stop. By directing oil to the rod side of the cylin-
der, the piston will be forced in the opposite direction and
the cylinder rod will retract.
Systems Incorporating Holding Valves
Holding valves are used in the - Lift, Telescope, Lockout,
and Slave Level circuits to prevent retraction of the cylin-
der rod should a hydraulic line rupture or a leak develop
between the cylinder and its related control valve.