JLG 3246E2 Service Manual - Manual (Page 15)

SECTION 2 - PROCEDURES
3120855 – JLG Sizzor – 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, except as recommended, as they may not
contain the same required additives or be of compa-
rable viscosities. Good grade mineral oils, with vis-
cosities suited to the ambient temperatures in which
the machine is operating, 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, 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° C (-15° F). is not recommended. If it is
necessary to start the system in a sub-zero environ-
ment, it will be necessary to heat the oil with a low
density, 100VAC heater to a minimum temperature of
-26° C (-15° F).
3. The only exception to the above is to drain and fill
the system with Mobil DTE 13M oil or its equivalent.
This will allow start up at temperatures down to -29°
C (-20° F). However, use of this oil will give poor per-
formance at temperatures above 49° C (120° F). Sys-
tems using DTE 13M oil should not be operated at
temperatures above 94° C (200° F) under any condi-
tion.
Changing Hydraulic Oil
1. Use of any of the recommended crankcase or
hydraulic oils increases JLG’s recommended oil
change interval to 800 hours. However, filter ele-
ments must be changed after the first 50 hours of
operation and every 400 hours thereafter. When
changing the oil, use only those oils meeting or
exceeding the specifications appearing in this man-
ual. If you are unable to obtain the same type of oil
supplied with the machine, consult your local sup-
plier for assistance in selecting the proper equiva-
lent. Avoid mixing petroleum and synthetic base oils.
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 Table 1-2 for an explanation of the lubricant
key designations appearing in the Lubrication Chart.
2.4 CYLINDERS - THEORY OF OPERATION
Cylinders are of the double acting type. The Steer sys-
tems incorporate double acting cylinders. A double acting
cylinder is one that requires oil flow to operate the cylinder
rod in both directions. Directing oil (by actuating the corre-
sponding 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 the rod will stop. By
directing oil to the rod side of the cylinder, the piston will
be forced in the opposite direction and the cylinder rod
will retract.
A holding valve is used in the Lift circuit to prevent retrac-
tion of the cylinder rod should a hydraulic line rupture or a
leak develop between the cylinder and its related control
valve.
2.5 VALVES - THEORY OF OPERATION
Solenoid Control Valves (Bang-Bang)
Control valves used are four-way three-position solenoid
valves of the sliding spool design. When a circuit is acti-
vated and the control valve solenoid energizes, the spool
is shifted and the corresponding work port opens to per-
mit oil flow to the component in the selected circuit, with
the opposite work port opening to reservoir. Once the cir-
cuit is deactivated (control returned to neutral), the valve
spool returns to neutral (center) and oil flow is then
directed through the valve body and returns to reservoir. A
typical control valve consists of the valve body, sliding
spool, and two solenoid assemblies. The spool is
machine fitted in the bore of the valve body. Lands on the
spool divide the bore into various chambers, which, when
the spool is shifted, align with corresponding ports in the
valve body open to common flow. At the same time other
ports would be blocked to flow. The spool is spring-
loaded to center position, therefore when the control is