TM 10-3950-672-24-2
A rod knock occurs when the engine is not loaded.
Verify by first applying load and then unloading and
listening for the knock.
Crankshaft and Main Bearings
Improper maintenance of the lubrication system is also
the primary cause of reduced main bearing life.
A malfunction of the crankshaft/main bearing will usually
be detected by reduced oil pressure. As with rod
bearings, continued operation with low oil pressure will
eventually will produce a knocking sound.
A main bearing will be heard when the engine is loaded.
A damaged or worn thrust bearing flange of the upper
main bearing shell can be detected by measuring the
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