Knock Diagnosis

Knock Diagnosis
Definition for Knock
Engine knock refers to various types of engine noise. Heavy knock is usually very loud and the result of broken or excessively worn internal engine components. Light knock is a noticeable noise, but not as loud. Light knock can be caused by worn internal engine components. Loose or broken external engine components can also cause heavy or light knock.

Engine Knocks Cold and Continues for Two-Three Minutes and/or Knock Increases with Engine Torque

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^ Cold engine piston knock usually disappears when the cylinder is grounded out. Cold engine piston knock, which disappears in about 1.5 minutes, is considered acceptable.

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Heavy Knock Hot with Torque Applied

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Light Knock Hot

Knocks during Initial Start-Up But Lasts Only a Few Seconds

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^ When the engine is stopped, some valves will be open. Spring pressure against the lifters will tend to bleed the lifter down. Attempts to repair this should be made only if the problem is consistent. An engine that is operated for only short periods between start-ups may have lifter noise that lasts for a few minutes. This is a normal condition.

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Knocks at Idle Hot