TM-9-2815-200-35 Maintenance Manual for AVDS-1790-2M AVDS-1790-2A and AVDS-1790-2AM Engines Download
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e. Ball and Needle Bearings. (1) Bearings require special attention in cleaning and oiling. After removing the surface dirt, oil, or grease, the bearings, except the sealed, permanently lubricated type, should be placed in hot oil (about 150°F.) to loosen congealed oil and grease. After cleaning, the bearings should be coated with a film of lubricant and wrapped tightly in oiled or waxed paper until inspection and assembly. Note. Do not immerse sealed type ball bearings in dry-cleaning solvent, mineral spirits paint thinner, or hot oil. Entrance of cleaning agent will destroy lubricants sealed in bearing at time of manufacture. Loss of lubricant will result in premature failure of bearing and possible severe damage to the engine. (2) Clean sealed ball bearings by wiping the exterior surfaces with a clean cloth moistened in dry-cleaning solvent. Compressed air must never be used in cleaning or drying of ball or needle bearings. Damage to bearings will result from spinning of bearing by air blast. (3) Refer to TM 9-214 for information on inspection, care, and maintenance of bearings. f. Painted Parts. The reconditioning of painted parts should be a matter of good judgment. Parts that appear to be in good condition after cleaning, need not be stripped and repainted in their entirety, but should be cleaned and designated for touch-up only. Parts that are rusted, or otherwise devoid of paint, must be stripped to bare metal. Rubber com- position shroud seals must be removed and discarded before the parts can be stripped of paint. 6-3. Inspection a. General. The engines are precision built, and the overhaul standards tables listed in this chapter have been fixed at extremely close limits. The following general instructions apply to all inspection procedures. (1) Use modern methods and equipment such as magnaflux, zyglo and ultrasonic in- spection for inspecting component parts where cracks and other damage cannot be detected visually. (2) Extreme care must be exercised in all phases of inspection. Inspect components following instructions in paragraph b. (3) Inspect finish of all parts. Mark all parts that require refinishing. b. Overhaul Standards. To identify parts, the Overhaul Standards Tables of this chapter refer to the exploded views in the repair parts section (Appendix B). Key letters are used on the ex- ploded views to locate points of measurement for overhaul limits. Each table contains the maximum, minimum, and key clearances of new or overhaul parts. The clearances, listed mainly for reference, will automatically be achieved if the mating parts are within the dimensional tolerances listed in the tables. In some cases, a part that is out of dimensional tolerance may be used, providing the mating part has been carefully selected and, when mated, is within the maximum clearance limits specified in the wear limits column of the tables. The wear limits indicate the point at which parts may be worn before replacement, in order to assure maximum service and minimum replacement. Normally all parts which have not worn beyond dimensions shown in the “Wear limits” columns or are damaged from corrosion, will be approved for service. (1) Symbols employed in the Overhaul Standards Tables are identified as follows: *-An asterisk in the “Wear limits” column indicates that part must be replaced when worn beyond the limits given in the “Sizes and fits of new parts” column. L-The letter “L”, following the tolerance dimensions given in the “Sizes and fits of new parts” column and the “Wear limits” column, indicates a loose fit (clearance). T-The letter “T”, following the tolerance dimensions given in the “Sizes and fits of new parts” column and the “Wear limits” column, indicates a tight fit (interference). (2) The following is a check list of parts to be magnetic-particle or flourescent-penetrant inspected: 6-2