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The exterior of the engine, and its attached components, can be cleaned with a suitable cleaning solvent, such as P-D-680. If the solvent is sprayed on the engine with compressed air, care must be taken to avoid forcing dirt, solvent, or moisture into engine openings and electrical connections. The primary purpose of cleaning is to remove contaminants that might conceal minor cracks and defects which if not detected could eventually lead to failure. Under normal circumstances, engine components are cleaned only as necessary to perform required inspection and repair. After using alternate or emergency fuels, cleaning internal hot-end parts may be required to remove lead oxide deposits. These deposits, if not removed, are detrimental to engine life and performance. The choice of any particular cleaning agent or process depends upon the engine part to be cleaned and the contaminants to be removed.

Take particular care in selecting a cleaning method to ensure that anodizing or dichromating is not removed from the surfaces. Do not use caustics on aluminum, magnesium, ceramic-coated, aluminized, painted, nitrated, or carbonized parts. In most cases the engine manual prescribes the approved cleaning procedure to be used. Most engine parts may be cleaned by using the following methods.

a. Vapor degreasing. Used only on unpainted metal parts or aluminum-painted steel parts, vapor degreasing using heated trichloroethylene, type II, or perchloroethylene, specification No. O-T-634, removes oil, grease, and sludge. The hot vapor condenses on metal surfaces, liquefies, and carries away the oil, grease, and sludge. Parts may be flushed while held in the vapor. To prevent corrosion, the parts should not be removed from solvent vapors until they have reached the temperature of the vapor.

b. Solvent immersion. In another cleaning method, the parts are immersed in Carbon Removing Compound MIL-C-19853, to remove carbon, gum, grease, and other surface contaminants. This method is used on steel and stainless steel parts. Parts with painted finishes should not be cleaned by this method, because the carbon cleaning compound attacks the paint.

c. Vapor blasting. An abrasive method used to clean combustor parts, vapor blasting must not be used on ceramic, magnesium, painted, or aluminum surfaces. Be sure that metal is not removed during cleaning and that cooling slots, holes, ridges, and overlap areas do not become clogged with blasting grit.

d. Dry-cleaning solvent. All metal parts may be cleaned with dry-cleaning solvent, P-D-680 Type I. This method is suitable for removing heavy oil and grease deposits from most parts, including flexible hoses and carbon seals. Dry-cleaning solvent leaves an oily film that protects steel parts from corrosion for a short time.



David L. Heiserman, Editor

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Revised: June 06, 2015