the engine. However, the air silencer or air inlet housing must be removed.

CAUTION

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 SPEED ONLY.

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 seal leakage.

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 exists.

Excessive backlash in the blower timing gears usually results in rotor lobes rubbing throughout their length.

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 thoroughly.

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 manufacturer's 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 air pressure.

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.