I have a 2001 A6 2.7T Tip at 685xx miles

in the morning when i turn the car on the car rattles and makes wierd deep sounding muffling noise's. not to sound like an idiot but its like mum mum mum mum mum fallowed by a series of ticking and then after a while it goes away.

Upod driving the car upon any start up, within the first 15-20 seconds of driving and getting some throttle the car makes a sudden but very momentary blip noise like a little siren but only for a split second... then i dont hear it again untill i park the car and start t up and take it for another drive.

My coolant temperature gauge i have noticed isnt moving.... it sits at zero all day i dontknow whether or not the thermo stat is shot or the gauge is busted.

i have not done any services since only the basic oil and filter stuff

 

might need to look into a thermo

but i was thinking it could be a pump or something, casue these cars are made to warm the exhaust up, that is what i was thinkig

 

My old 2.8 did that when my flex pipes went. but I donno if that would be your problem. also my cats went bad. but they get replaced with the flex.