Hello i have a 2002 a4 1.8t and i have noticed here latley that while my car is idling for more that a couple minutes the turbo spools down like when the car is turned off. I have never noticed this before and would just like to know if this is normal. Thanks.

 

Are you sure it is the turbo? With your car idling the turbo shouldn't really be doing anything to spool down from. Plus you really shouldn't be able to hear your turbo anyway, at least not obviously. I suspect your are hearing something else. Most likely SAI pump

 

Definately not the turbo, i think you have a leak in the SAI line. The SAI pump will activate when the engine is cold, and it kinda sounds like a vacuum cleaner when there is a leak. Get under the car, take off the belly pan and locate the SAI pump on the passenger's side. Its a large black box with flexible plastic hoses going into it that run up to the air box, disconnect the connector and you should hear the noise stop. Then just follow those hoses until you find the leak.
If no leak can be found the bearings inside the SAI pump are going out. You can try to take it apart and lube the bearings or buy a new pump. (not cheap)

 

Ill have to look into it. I noticed the aound when i first bought the car but it only made the noice when i turned off the car. I assumed it was the excess turbo spooling out but it makes sense that at an idle the turbo isnt doing anything. Ill look into the sai pump and see what i can find. Thanks for the help.