Figure 3-7.—Errors to avoid when taking liner measurements.Figure 3-8.—Trace of caliper end when determining the truediameter of a liner.practice for two persons to take the liner measurement;then any discrepancy between the two sets of readingscan be rechecked.CausesExcessive or abnormal wear of cylinder liners maybe caused by insufficient lubrication, dirt, improperstarting procedures, or low cooling water temperature.The lubricating system must be carefullymaintained in proper working order. The method ofcylinder liner lubrication varies with different engines.The proper grade of oil, according to enginespecifications, should be usedThe engine must not be operated in a dirty condition.The air box, crankcase, and manifold should be cleanedand maintained in a clean condition, to avoid cylinderwear and scoring. (Attention to the air cleaner, oil filters,and oil centrifuge are the best precautions against theentrance of dirt into the engine.)Improper starting procedures will cause excessivewear on the liners and pistons. When an engine is firststarted, some time may elapse before the flow oflubricating oil is completed; also, the parts are cold andcondensation of corrosive vapors is acceleratedaccordingly. These two factors (lack of lubrication andcondensation of corrosive vapors) make the periodimmediately after starting a critical time for cylinderliners. If an independently driven oil pump is installed,it must be used to prime the lube oil system and buildup oil pressure before the engine is started The engineshould not be subjected to high load during the warm-upperiod. Follow the manufacturer’s instruction manualconcerning warm-up time and load application for theengine concernedThe cooling water of an engine should always bemaintained within the specified temperature ranges. Ifthe temperature is allowed to drop too low, corrosivevapors will condense on the liner walls.RepairsCylinder liners worn beyond the maximumallowable limit should be replaced. You will find themaximum allowable wear limits for engines in theappropriate manufacturer’s technical manual or theDiesel Engine Wear Limit Chart available from theNaval Sea Systems Command. In the absence of suchspecific information, the following wear limits(established by NAVSEA) apply in general to1. two-stroke cycle engines with aluminumpistons: 0.0025 inch per inch diameter,2. slow-speed engines over l8-inch bore: 0.005inch per inch diameter, and3. all other engines: 0.003 inch per inch diameter.If you must remove a liner, follow the instructionsgiven on the appropriate maintenance requirement card(MRC) or in the manufacturer’s technical manual for theparticular type of engine. Figure 3-9 illustrates themethod generally used to remove a cylinder liner.To remove the cylinder liner, proceed as follows:1. Drain the water from the engine.2. Remove the cylinder head.3. Remove the piston(s).3-6
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