a6 allroad 2.5tdi v6 2004

[ms1083]

in the last few weeks car has started "whining" at about 2000rpm, stops above this. it sounds like the turbo but louder than normal, if I disconnect the vacuum hose to the turbo it still makes it so I assume its not the turbo.
it is less noisy if the aircon is not switched on but is still present.
could it be the tension on the belt for the aircon compresser? I changed it along with all the other belts, pullys, tensioners etc 1 year ago when did its timing belt but its the only belt which you can adjust the tension, could it be too slack or tight?
Or any other suggestions?
Otherwise all is fine, no fault codes. its not that loud, I don't think anyone else who doesn't know the "normal" sound of this car would notice it.

 

[adamss24]

It could be one of the auxiliary belt rollers- there are 3 different ones or it could be one of the rollers that drive the cambelt. I would take the bumper off and check each one by hand- take the aux. belt off and see if the noise stops, if it does then it's a cheap fix, if not then you're looking at a good few hundred quid to do a timing belt change...