A4 idle screech.

[3lward]

Just taken ownership of an 04 A4 Avant S-line 190 (BEX engine I believe) on idle it makes a horrible screech/grinding noise, it only lasts 2 seconds and goes. If I rev it it goes away which leads me to believe its some tensioner of sort but it seems to be coming from the back or right hand side of the engine, I've had a quick look at the tensioner and it does move alot on idle but then tensions under load. Any known problems in that area?

 

Thanks for your help.