Crankshaft Knocks Noises

Crankshaft Knocks Noises Points : crankshaft knocks noises, engine noise analysis, problems in internal combustion engines, ic, engine, auto diesel Noises classified as crankshaft knocks are usually dull, heavy, metallic knocks, which increase in frequency as the speed and the load on the engine increases, or they become more noticeable at extremely low speed when the engine is idling unevenly.

The most common crankshaft knock, due to excessive bearing clearance, is usually apparent as an audible “bump” under the following circumstances; when the engine is pulling hard, when a cold engine is started, during acceleration, or at speeds above 35 mph. if excessive clearance exists at only one or two of the crankshaft journals, the “bump” will be less frequent and less pronounced. Usually alternate short-circuiting of each spark plug will determine the approximate location of a loose bearing.

Excessive crankshaft end-play causes a sharp noise or rap which occurs at irregular intervals, usually at idling speeds, and in bad cases generally can be detected by the alternate release and engagement of the clutch. To detect a loose flywheel, advance the engine idle to a speed equivalent to 10 to 15 mph. turn off the ignition switch and then, when the engine has almost stopped, turn the switch on. If the operation is repeated several times and if, of course, the flywheel is loose, one distinct knock will be noted every time the switch is turned on. At low engine speeds with an uneven idle, a loose timing gear generally can be detected by a sharp clatter. When testing for either of these conditions, short circuit one or two spark plugs to produce an extremely uneven idle.