Love my A6, 2004 2.7 bought with 115000 miles in May this year. Shortly after purchase, came across a "hot start" problem but was able to diagnose it to the water temp sensor thanks to the help of this forum. Problem solved!
Now, since the temperatures have cooled in the Detroit area, I'm hearing a whining noise comiong from the motor compartment on start up and lasting about 1 or 2 minutes, then stopping. It doesn't happen everytime but may start again after the car runs a few minutes but stops again. 2 times is about all I count before it stops completly. Does not seem to affect performance, car runs strong. Just this weird noise that comes and goes.
Any ideas? You can definately hear it spool down when the noise goes away.
All the temps seem normal and the heater blower works fine.

 

Probably your secondary air injection unit (SAIU), part of emissions. I think it stuffs extra air into the exhaust in cooler weather. If it is just whining for 30-120 seconds, you are ok. If it makes noise like a blender wih pebbles in it, like mine recently started doing, not so good. I said screw it and had it disconnected, and live with the CEL. PS - Also in MI.

 

Thanks for the reply. Sounds to be similar to what I'm experiencing. No gravel noise yet so I'll live with it for now. As I mentioned, the car runs great as is.