If inspection reveals signs of water in an engine or
in the exhaust manifold, take steps immediately to
correct the trouble. Check the unit for proper
installation. Wet-type silencers must be installed with
the proper sizes of piping. If the inlet water piping is too
large, too much water may be injected into the silencer.
There must be continuous-type water drains on the
silencer. If a silencer has no continuous drain and if the
engine is at a lower level than the exhaust outlet, water
may back up into the engine.
Dry-type silencers may become clogged with an
excessive accumulation of oil or soot. When this occurs,
exhaust back pressure increases, causing troubles such
as high exhaust temperature, loss of power, or possible
stalling. A dry-type silencer clogged with oil or soot is
also subject to fire. Clogging can usually be detected by
fire, soot, or sparks coming from the exhaust stack An
excessive accumulation of oil or soot in a dry-type
silencer may be due to a number of factors, such as
failure to drain the silencer, poor condition of the engine,
or improper engine operating conditions.
Insufficient Intake Air
Insufficient intake air, which may cause an engine
to stall or stop, may be due to blower failure or to a
clogged air silencer or air filter. Even though all other
engine parts function perfectly, efficient engine
operation is impossible if the air intake system fails to
supply a sufficient quantity of air for complete
combustion of the fuel.
CLOGGED AIR CLEANERS AND SILEN-
CERS.Sometimes an engine will fire erratically or
misfire because of a clogged air cleaner or silencer. Air
cleaners must be cleaned at specified intervals, as
recommended in the engine manufacturers technical
manuals. A clogged cleaner reduces the intake air,
thereby affecting the operation of the engine. Clogged
air cleaners may cause not only misfiring or erratic firing
but also such difficulties as hard starting, loss of power,
engine smoke, and overheating.
When you clean an air cleaner element, if you use a
volatile solvent, be SURE the element is dry before you
reinstall it on the engine. Volatile solvents are excellent
cleaning agents but, if permitted to remain in the filter,
may cause engine overspeeding or a serious explosion.
Oil-bath type air cleaners and filters cause very little
trouble if serviced properly. Cleaning directions are
usually given on the cleaner housing. The frequency of
cleaning is usually based on a specified number of
operating hours, but more frequent cleaning may be
necessary where unfavorable conditions exist.
When you fill an oil bath-type cleaner, follow the
manufacturers instructions. Most air cleaners of this
type have a FULL mark on the oil reservoir. Filling
beyond this mark does not increase the efficiency of the
unit and may lead to serious trouble. When the oil bath
is too full, the intake air may draw oil into the cylinders.
This excess oil-air mixture, over which there is no
control, may cause an engine to run away, resulting in
BLOWER FAILURE.Troubles that may prevent
a centrifugal blower from performing its function
usually involve damage to the rotor shaft, thrust
bearings, turbine blading, nozzle ring, or blower
impeller. Damage to the rotor shaft and thrust bearings
usually results from insufficient lubrication, an
unbalanced rotor, or operation with excessive exhaust
Centrifugal blower lubrication problems may be
caused by failure of the oil pump to prime, low lube oil
level, clogged oil passages or oil filter, or a defective
relief valve, which is designed to maintain proper lube
If an unbalanced rotor is the cause of shaft or bearing
trouble, there will be excessive vibration. Unbalance
may be caused by a damaged turbine wheel blading or
by a damaged blower impeller.
Operating a blower when the exhaust temperature
is above the specified maximum safe temperature
generally causes severe damage to turbocharger
bearings and other parts. Make every effort to find and
eliminate causes of excessive exhaust temperature
before the turbocharger is damaged.
Turbine blading damage may be caused by
operating with an excessive exhaust temperature,
operating at excessive speeds, bearing failures, failure
to drain the turbine casing, the entrance of foreign
bodies, or by turbine blades that break loose.
Damage to an impeller may be caused by thrust or
shaft bearing failure, entrance of foreign bodies, or
loosening of the impeller on the shaft.
Since blowers are high-speed units and operate with
a very small clearance between parts, minor damage to
a part could cause extensive blower damage and failure.
Although there is considerable difference in
operating principle and construction between the
positive-displacement blower (Roots) and the