HYDRAULIC SYSTEM
SUBSECTION 5A
7. All containers and funnels used in handling hydraulic oil
must be absolutely clean. Use a funnel with a 200 mesh
clutches, proceed as follows,
screen for filling the hydraulic oil reservoir. and fill the res-
1. Starr the engine and build up pressure in the control sys-
ervoir only through the filler opening. The use of cloth to
tem.
strain the oil should be avoided to prevent lint from getting
2. Shut the engine off and actuate the control valve to re-
into the system.
lieve most of the pressure. The pressure gauge should show
8. When removing any hydraulic component, be sure to cap
only a small amount of pressure remaining in the system.
and tag all hydraulic lines involved. Also plug the ports of
3. Begin wrth the lowest hydraulic cylinder and work to-
the removed components.
ward those cylinders at the highest point. The appropriate
valve will have to be actuated when bleeding the cylinders.
9. All hydraulic components must be disassembled and as-
sembled in spotlessly clean surroundings. During disas-
4. Close the bleeder fitting when the air has been removed
sembly, pay particular attention to the identification of parts
frorn that Iine.
to assure proper reassembly. Clean all metal parts in a clean
5. Remove the bleeder hose and repeat the procedure on
mineral oil solvent. Be sure to thoroughly clean all internal
the next highest cylinder.
passages. After the parts have been dried thoroughly lay
6. All clutches should be rotated so that the cylinders are at
them on a clean, lint-free surface for inspection.
their highest position.
10. Replace all O-rings, back-up rings, and seals when
overhauling any component. Lubricate all parts with clean
hydraulic oil before reassembly. Use small amounts of
GENERAL MAINTENANCE
petroleum jelly to hold O-rings in place during reassembly.
The following points should be kept in mind when working
on the hydraulic system or any hydraulic component.
11. Be sure to replace any lost hydraulic oil when com-
1. Any structure has limits of strength and durability. To
pleting the installation of the repaired component, and
prevent the failure of structural parts of hydraulic com-
bleed any air from the system when required.
ponents, an unloading valve which limits pressure to safe
operating limits for the accumulator and a relief valve which
12. All hydraulic connections must be kept tight. A loose
Iimits pressure to safe operating limits for crawler exten-
connection in a pressure line will permit the oil to leak out or
sion are included in the hydraulic circuit. The setting of
air to be drawn into the system. Air in the system can cause
these valves must never be changed.
damage to the components and noisy or erratic system op-
2. Tolerances of working parts in the hydraulic system are
eration.
very close. Even small amounts of dirt or foreign material in
the system can cause wear or damage to components, as
well as generally faulty operation of the system. Every
precaution must be taken to assure absolute cleanliness of
TROUBLESHOOTING GUIDE
the hydraulic oil.
3. Samples of hydraulic oil should be drawn from the res-
GENERAL. The troubleshooting charts and maintenance
ervoir every SiX months. These samples should be about two
hints that follow are of a general nature, but should provide
quarts, and should be taken while the oil is warmed through
an intuitive feeling for a specific system.
normal operation. If possible, the sample should be
analyzed by a qualified lubrication specialist to determine
whether it is suitable for further use. The interval between
KNOWING THE SYSTEM. Probably the greatest aid to
oil changes depends on operating conditions and on the
troubleshooting is knowing the system Every component
care used in keeping the oil clean.
has a purpose in the system. The construction and oper-
ating characteristics of each should be understood. Know
4. Whenever there is a hydraulic component malfunction
how the system works and what the valve settings and
which gives reason to believe that there are metal particles
pump output should be.
or other foreign materials in the system, drain and flush the
entire system and replace the filter cartridges. A complete
change of hydraulic oil must be made under these circum-
The crawler extension circuit has a relief valve pressure
stances.
gauge port to allow checking of pressure. Always set and
5. Whenever the hydraulic system is drained, check the
check the pressure with a gauge that IS known to be accu-
magnetic drain plug for metal particles. If metal particles
rate. The question may arise as to what the correct oper-
are present, flush the system and add a new change of oil.
ating pressure of this circuit is. If it IS not specified, the cor-
The presence of metal particles also may indicate the
rect operating pressure is the lowest pressure which will
possibility of imminent component malfunction.
allow adequate performance of the system function and still
remain below the maximum rating of the components.
6. Do not use synthetic or fire resistant oils in this ma-
Once the correct pressures have been determined, note
chine. The packings in this system are designed for a good
them for future references.
grade mineral oil.
5A-2
