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TM-9-2815-200-35 Maintenance Manual for AVDS-1790-2M AVDS-1790-2A and AVDS-1790-2AM Engines Download

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6-24. Cleaning a. Pistons. (1) Clean pistons (9.3, fig. B-4) and piston pins (9.2) by soaking in carbon removing compound, Specification MIL-S-12382 (Ord Type 1). Warning: Use goggles, rubber gloves, and rubber apron when cleaning parts in carbon removing compound. Provide adequate ven- tilation. Avoid inhalation of fumes and skin contact. If compound is splashed on skin, flush with fresh water and wash with alcohol. Alcohol containing 2 to 3 percent camphor is preferable. (2) Optional cleaning of the piston can be accomplished with a vapor blast using glass heads to provide the cleaning action and surface roughness. A surface roughness of 50 to 100 RMS is exceptable with a RMS of 80 preferred. If vapor blast equipment is not available, scrape off remaining carbon deposits from piston ring grooves with a scraper or broken piston ring. Be careful not to scratch or gouge ring lands on piston. Clean oil drain holes and oil ring grooves in piston. Remove carbon from oil holes in ring grooves. Clean carbon from piston pins with crocus cloth dipped in dry-cleaning solvent or mineral spirits paint thinner. 6-25. Inspection a. Pistons. Inspect piston for cracks, flaws or distortion. Use a magnifying glass and a strong light. Small cracks will show under the light as irregular or dark streaks. Check piston ring grooves against limits specified in overhaul standards (table 6-13). Inspect piston for dam age or broken ring lands, nicks, burrs, or scratches. Inspect piston pin bores for wear, cracks, or abrasions. Replace piston if found unserviceable. b. Piston Rings. Inspection of piston rings rem oved from piston is not required. New rings will be installed during piston assembly. c. Piston Pins and Plugs. Inspect piston pin and plugs for cracks, nicks, or wear. Inspect end plugs for large wear pattern and replace if found unserviceable. Check diameter of pins against limits specified in overhaul standards (table 6- 13). 6-48