Engine Squeak on Cold Start

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Engine Squeak on Cold Start

All Models with the M54 engine


On a cold start there is a squeak from the front of the engine that only lasts for several moments after startup, once the engine warms up the noise usually goes away.


The noise is caused by the alternator belt tensioner and/or deflection pulleys. The pulleys become worn and start to make noise during initial startup.


Replacement of the tensioner and/or deflection pulleys is the only fix. To determine if the pulley is noisy is to spin it at a high rate of speed with compressed air. A faulty pulley would make a high pitch squeak or growling noise. The original belt tensioning design was with a mechanical spring tensioner and a pulley, on this design the tensioner pulley cannot be replaced separately and is no longer available. An updated tensioner design has been implemented, a hydraulic tensioner setup where the tensioner pulley can be separately replaced.

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