SUBSECTION 5A
HYDRAULIC SYSTEM
GENERAL
7. Cycle the machine through all crane functions
The hydraulic control system, as defined for this manual, in-
cludes all the hydraulic control components on the upper of
the machine and the crawler extension system, The items
BLEEDING THE HYDRAULIC SYSTEM
included in this system are the pump, control valves, actuat-
ing cylinders, and related components. The propel hydrau-
GENERAL. When air is present in the hydraulic system, the
lics is covered in Section IX.
controls will be "spongy" and will not operate efficiently.
Air will enter the system if a control valve is removed or a
A hydraulic schematic of the complete hydraulic control
line is broken between a control valve and hydraulic cylin-
system, along with a description of system operation, is at
der. The following statements apply to all bleeding oper-
the rear of this subsection.
ations:
FLUSHING THE HYDRAULIC SYSTEM
1. Check all fittings, hoses and lines for leaks.
If any evidence of hydraulic system contamination, such as
2. Hydraulic oil should be visible in the sight gauge of the
dirt, sludge, and/or metallic particles is discovered, flush
hydraulic reservoir. Fill as necessary with the oil specified
and clean the system as follows. If the cause of the con-
in Section III.
tamination is due to a faulty component the component
3. Normally it is not necessary to bleed the lines or valves
must be repaired or replaced before the hydraulic system is
(except those for the right and left drum brakes) on the con-
flushed.
trol stand, all bleeding is to be done at the respective slave
NOTE
cylinders.
The hydraulic oil should be warmed before the reser-
voir is drained.
1. Locate the machine on a flat, level surface.
Hydraulic oil must not come in contact with
2. Remove the drain plug and drain the oil into a suitable
any brake or clutch lining during bleeding op-
container. Allow sufficient time for all the oil to drain from
erations. If this does occur, replacement of the
the walls of the reservoir.
linings will be necessary.
3. Install the dram plug. Fill the reservoir with a 50-50 mix-
ture of kerosene and clean hydraulic oil.
4. Cylinder bleeding is best accomplished by using a clear
4. Cycle the machine through all crane functions. It is im-
plastic hose attached to the bleeder fitting with its other
portant that all valves be operated so that the new oil goes
end at the bottom of a partially filled jar or can of hydraulic
through all lines.
oil to prevent air from entering the bleeder hose. The
5. Circulate the oil through the system until inspection
bleeder fittings should only be opened when the cylinders
shows the equipment to be in satisfactory condition, or until
are under some amount of pressure.
it is obvious that the system will have to be disassembled
5. After the bleeding operation is completed, recheck the
and cleaned manually.
oil level. Refill the reservoir to bring oil levels to the upper
6. Remove the drain plug and drain the flushing oil from the
half of the sight gauge with all hydraulic cylinders fully re-
reservoir. Remove the filter from the top of the reservoir and
tracted and the engine off.
clean the inside of the reservoir manually. Reinstall the
6. The procedure as described is for bleeding the entire hy-
drain plug and the reservoir filter. Refill the reservoir with
draulic control system. If only a portion of this circuit re-
clean hydraulic oil. Be sure to clean the system return fil-
quires bleeding, only the steps which apply must be fol-
ters and change the outlet filter element before refilling the
lowed to bleed that portion of the circuit.
system.
5A-1
