TM 5-3810-306-34
BLEEDING AIR FROM HYDRAULIC SYSTEM
TOOLS: None
SUPPLIES: None
EQUIPMENT CONDITIONS: None
GENERAL:
NOTE
By design, air entering the hydraulic oil will normally
A soap solution applied to the fittings
be removed automatically by passage of the oil over
and joints may also prove helpful in
the baffles in the hydraulic reservoir. However, air
detecting small leaks while the
can enter the system if a component has been
system is pressurized.
replaced, the reservoir level is too low, or a leak
develops in the suction lines to the pumps. If air
c. Inspect all joints and fittings for evidence of
becomes entrapped in the hydraulic oil, it may be
leaks.
detectable
in
pumps
and
motor-operated
components such as the swing mechanism and
d. Remove pressure, repair any leaks found and
hoist(s) causing these units to become noisy during
reopen any openings (vents, etc.) closed for
operation. Should noisy operation occur, first check
inspection.
oil level in hydraulic reservoir and fill as necessary.
Then inspect for leaks in suction lines leading to
e. Refill reservoir after completing any repairs or
pumps.
service.
Small leaks may be difficult to locate. Should you
f. Operate all hydraulic circuits several times in
encounter a leak that is not readily detectable, the
both directions. This action should return any
following method may be used when checking for
entrapped air to the reservoir where it can be
such leaks.
removed from oil by the baffle system provided.
1. PRESSURIZE HYDRAULIC SYSTEM.
2. REMOVE ENTRAPPED AIR IN CYLINDERS.
a. Seal all normal openings (vents, etc.) in
CAUTION
hydraulic system and reservoir.
Locate crane on a firm supporting
b. Using a positive means to control pressure (i.e.,
surface and position boom in most
a regulator), pressurize hydraulic system to 2 to
stable position when extending boom
4 psi (13.79 to 27.6 kPa/0.1379 to 0.276 bar).
at low angles.
13-117
