the engine. However, the air silencer or air inlet housing
must be removed.
When a blower on an engine is being
inspected with the engine running, keep your
fingers and clothing away from moving parts of
the blower. RUN THE ENGINE AT LOW
Dirt or chips, drawn through the blower, will make
deep scratches in the rotors and housing and throw up
burrs around these abrasions. If the burrs cause
interference between rotors or between rotors and
blower housing, remove the blower from the engine and
dress down the parts to eliminate this interference.
Replace the rotors if they are too badly scored.
Oil on the blower rotors or on the inside surfaces of
the blower housing indicate rotor shaft oil seal leaks. To
confirm your finding, run the engine at a low speed
while shining a light into the rotor compartment. A film
of oil radiating away from the rotor shafts shows the oil
A worn blower drive results in a rattling noise inside
the blower. You can detect this condition by grasping the
top rotor firmly and attempting to rotate it. The rotor may
move from three-eighths to five-eighths inch, measured
at the lobe crown. When released, the rotor should move
back at least one-fourth inch. If the rotor cannot be
moved this distance or if the rotor moves too freely, the
flexible blower drive coupling should be inspected and
if necessary, replaced.
If a check shows the drive coupling to be worn,
remove the blower drive assembly from the cylinder
block end plate. After the blower has been removed from
the engine, remove the drive gear hub bearing
support-to-cylinder block end plate bolts.
Loose rotor shafts or damaged bearings will cause
rubbing and scoring between the following components:
the crowns of the rotor lobes and the mating rotor roots,
the rotors and the end plates, or the rotors and the blower
housing. Generally, a combination of these conditions
backlash in the blower timing gears
in rotor lobes rubbing throughout their
To correct any of the above conditions, remove the
blower from the engine and either repair it or replace it.
The blower inlet screen should be inspected
periodical y for dirt accumulation. After prolonged
operation, dirt accumulation affects the airflow. Wash
the screen thoroughly in clean fuel oil and clean it with
a stiff brush until no dirt remains.
The air box drains should always be open. Check
them regularly and make sure the passages are clean. If
the liquid collects on the air box floor, a drain tube may
be plugged. Remove the cylinder block handhole
covers. Wipe the dirt out with rags or blow it out with
faltered compressed air. Then remove the drain tubes and
connectors from the cylinder block and clean them
Blower Removal and Disassembly
After you inspect the blower and determine what
you need to do to recondition it, remove and disassemble
the blower. Follow the instructions in the
manufacturers maintenance and repair manual.
After you remove the assembly, disassemble it and
be careful not to damage any parts. Use the proper tools
and follow the recommended disassembly procedures,
particular y when the blower drive, driven gears, and
timing gears from the rotor shafts are removed. Pull
them from the rotor shaft at the same time or you will
damage the rotors.
Cleaning, Inspecting, and Reassembly
After the blower has been disassembled, wash all
the parts in cleaning solvent or clean fuel oil. Then
blow-dry them, using filtered compressed air. Inspect
the parts before reassembly.
Wash the bearings by rotating them by hand in either
cleaning solvent or fuel oil until they are free from
grease and foreign matter. Clean the balls (or rollers) and
races by directing air through the bearings, at the same
time, rotating them by hand. Do not spin the bearing with
After thoroughly cleaning the bearings, rotate them
again by hand and inspect it for rough spots. The
bearings should run free. They should not show
indications of roughness. The double-row bearings are
preloaded and have no end play. A new double-row
bearing will seem to have considerable resistance to
motion when revolved by hand.
Check oil seals in the end plates. If necessary,
replace them, when the blower is being reconditioned
which is the recommended time to install new seals.