Drive belt buzzing

[Andrew Sheldon]

I have a late 2005 E85 2.0 Z4. I have had a buzzing noise for ages at a very particular part of the rev range, it would only buzz within that range and would completely disappear either side. It sounded like the heat shield vibrating and I was forever bending areas that I thought might have been the problem.
Yesterday I got my brother to have a look whilst I created the buzz noise and pinpointed it being the top part of the belt, you could clearly see it vibrating so fast it created this awful sound that I have had to live with for the last year or so.
My question is has anyone else had this problem and does anyone know how to fix it. I believe its had a new belt 2 or 3 years ago and the tensioner seems to be doing its thing. Any advise will be gratefully received.

 

[grannyknot]

No, can't say I have heard of that one before, is it vibrating in the middle of the belt between two pulleys?
Sounds like either the belt has a flaw in the webbing or the belt isn't tight enough.
A new belt doesn't cost much.

 

[enuff_zed]

I would suspect the idler pulley. If it’s bearing has gone that would transmit vibration to the belt

 

[Andrew Sheldon]

No, can't say I have heard of that one before, is it vibrating in the middle of the belt between two pulleys?
Sounds like either the belt has a flaw in the webbing or the belt isn't tight enough.
A new belt doesn't cost much.

Yes this seemed mighty odd to me as well. At first I couldn't believe the belt could make such a noise until I saw it with my own eyes, the noise matched perfectly with the belt vibrating. It happened right in the middle top part of the belt, probably the best way to describe the vibration is if you blew across an elastic band and created a resonance.
Ive just ordered a new belt today as a first, and cheapest, start to the fix. If it works I will post and let peeps know.
Thanks for your input btw

 

[Andrew Sheldon]

I would suspect the idler pulley. If it’s bearing has gone that would transmit vibration to the belt

Just bought a new belt as a start to the fix and will have a good look at the idler pulley and tensioner. Thanks for your help