gasoline, or solvent and never use compressed air to dry
the element.
during a crew turnover. The effort to check the lube oils
is easier than explaining to the chain of command why
an engine or part of the power train locked up or seized.
Oil Bath Air Cleaners
ENGINE OIL
Oil bath air cleaners (fig. 1-38) draw air down a
center tube where it strikes the surface of oil in the oil
reservoir. As the air strikes the oil reservoir, most of the
particles in the air do not make the 180-degree-upward
turn. The dirt particles remain trapped in the oil. As the
air continues upward and passes to the filter element, the
smaller particles that bypassed the oil are trapped. The
air keeps the filter element soaked with oil by creating
a fine spray as it passes the reservoir. The air then makes
another 180-degree turn and enters the intake system of
the engine.
NOTE: It is the operators responsibility to keep the
oil cup filled to the proper level with the correct weight
of oil and to document when the oil is dirty or has
thickened, reducing its ability to clean particles from the
air.
LUBRICATION SYSTEM
The engine lubrication system (fig. 1-39) reduces
friction between moving parts, absorbs and dissipates
heat, seals the piston rings and cylinder walls, cleans and
flushes moving parts, and helps deaden the noise of the
engine.
Checking the lubrication oils on a piece of equip-
ment is part of the prestart check and the operators
responsibility. Also, it is a good professional practice
to recheck the lube oil levels after a lunch break or
Besides reducing friction and wear, engine oil acts
as a cooling agent by absorbing heat from the surfaces
over which it is spread. Engine oil carries heat to the
engine sump where it is dissipated. The water
circulating through an oil cooler also helps to reduce this
heat (not all engines have oil coolers).
Engine oil is also used as a sealing agent. It fills the
tiny openings between moving parts and cushions them
against damage and distortion from extreme heat.
Engine oil is very important as a cleaning agent. Grit
and dirt in engine parts are often removed by the oil
before damage can result. The foreign matter and the
greases in the bottom of the crankcase are evidence that
engine oil cleans. Some oils have chemicals, known as
additives, added to make them even better cleaners.
Oil Level Indicator
The oil level indicator consists of a rod, known as a
dipstick. The dipstick extends through a tube into the
crankcase (fig. 1-40). Marks on the dipstick indicate
when the crankcase is full or, if low, how much oil is
needed. To take readings, you should perform the
following procedure: pull the dipstick out, wipe the
dipstick with a rag, stick it back in, pull it out once again,
and note how high the oil level is on it. On some engines,
the correct oil level is achieved after the engine has
Figure 1-40.-Oil level indicator.
1-29