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Discussion Starter #1
lately since it has been cold I have a sound at idle, best way to describe it is a rattle that goes away as soon as you come off idle, it also pretty much goes away after the vehicle has been running for a while and is warm....failing water pump? belt tensioner? it sounds like it is coming from the front of the engine somewhere, but cant tell exactly where
 

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Discussion Starter #2
replaced idler and tensioner pulleys today, tensioner pulley bearing was dry but the sound did not seem to go away, maybe get a little better though.....could the tensioner be going bad?
 

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Could it be the vanos rattle that is pretty common with the m54 engines? There is a video of the "ball bearings in a paint can " rattle associated with worn vanos seals.

You're sure its not the rattle in the tail pipe from the butterfly valve?
 

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Discussion Starter #4
most of the vanos rattle videos show the symptoms around 3k RPM...this sound is only at idle, add 100 RPM's and it goes away! it also gets less and sometimes not at all when it is warm. the sound is definitely coming from the front of the engine somewhere so that eliminates the butterfly valve. It does have a mechanical tensioner, which I read was being replaced with a hydraulic as per a SIB......I pick up a new tensioner in a few hours for $50 so we will see if that solves the problem.
 

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Discussion Starter #5
replaced the tensioner, definitely quieter but not gone, ran it without the AC belt with no change, listened to the front of the motor using a long screwdriver as a stethoscope and could not find the source of the noise, I am kind of at a loss
 

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I wonder if it may have something to do with the weight of the oil that you're using. That may be stretching it though. Does the noise seem louder when the weather is colder?
 

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Discussion Starter #7
using M1 0/40 with about 5k miles on it. I just drove 200 miles towing my enclosed trailer and the sound is no different, drove fine, no idle issues, no power loss, no SES light, not running warm, not using or losing coolant or oil, Im kinda stumped, only think I can think of is maybe its the big pulley on the bottom right of the engine (under the airbox and alternator) or the WP pulley?
 
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