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Discussion Starter #1
I failed my state inspection the other day and that started an onslaught of upgrades and maintenance. I just finished replacing 02 sensors, control arms and filters ect… but now there is a high pitched sound during idle. My first instinct is that it’s a belt (It sounds just like it) but I know that there are many other things that could make that noise. Is there any indications I should look for that would point to something else? The Vanos maybe?

It’s a 2004 325I and I bought it at 65K 2 years ago and have not changed the belts yet. :tsk: I'm now at 80k :tsk: . Still, could it be anything else besides the belts?

I realize by reading my own post that I should just change the belts but I want to cover all my basses first.:p
 

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Discussion Starter #4
Friday I was on the highway and my alternatr/fan belt shredded to peices. I spent all day replacing the belt and installing Mayle control arms and the sound is still there. The guy at the parts store I go to suggested the idler pully. Im dis heartned at the thought of going back under the hood.

Ill replace bothe just incase.
 

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From your description. It sounds like a belt tensioner pulley or idler pulley. Next to check would be alternator or water pump. If you have a mechanics stethiscope you can source out the problem easily. If not, a 2 foot section of vacuum hose will work also. Just hold one end to your ear & the other end to the various pulleys. Hope you find your problem. Aslo, I almost forgot, If you spray silicone spray on the belt, does the sound go away? If it does, then replace your belt. Chas.
 

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does it sound like you have a supercharger? lol
 

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Discussion Starter #9
It sounds like a supercharger but without the bragging rights. Ill get some video up shortly. I do appreceate all the help om getting on this. I just replaced the belt and it really dosnt sound like its comming from the water pump. I do have a mechanics stethiscope and took a listne however my untrained ear was unable to pinpoint to location of the sound, maybe I should take another stab at it.
 

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Did you ever get this resolved?
 

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I have a similar sounding issue. Took the car in to a bmw tech and he said it was most likely the idler pulley, so that is definitely something I would check out.
 
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