Maybe you need belt dressing to silence it.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

Never use drive belt dressing. A new high quality drive belt will not make any noise, provided all the pulleys are aligned properly. Now, the pulley bearings could produce some noise if they are worn, but not the belt itself.

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Fred Hoelzle

Ferdman, thanks for the follow up... I know it is tough/impossible to diagnose via the computer. The car has ~110K miles on it. I am thinking it may be the idler and/or the tensioner.

As Ferdman said - never use belt dressing.

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Jim

Have not and will not use any type of belt dressing. I changed upper idler pulley, tensioner and new serp belt and I am still getting the whining noise. Any other suggestions?

Alternator bearing?

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1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible