Starting just two day ago, and happening 3 times since then, I've had a loud chattering coming from the engine. The best I can describe it is like a bad throw-out bearing, but is an auto. It happened once after a 30 minute drive, and I let it go. It came back when I got back in the car, but once the tranny shifted into 2nd gear above 2K rpm's it went away and didn't come back until tonight. Again, it was there after the same 30 minute drive I take all the time. SO after coming into work for an hour, I started the car and heard the chattering. popped the hood but couldn't pinpoint it. Sounded like ti was coming from the front of the engine, and I could almost "feel" the vibration. So then I made a slow circle around the parking lot to see if it RPM-dependant, and it is. So I parked it, and revved the engine slowly. I wasnt'watching the tach, but somewhere around 2 grand or higher it went away. Turned the car off then on again, and it was gone.
Any idea what this might be?
The car is an '04 A6 2.7T with 66,575 miles.
A mechanic I spoke to in the fall said when water pumps are getting ready to fail, they'll occasionally make a chattering noise that people usually ignore.
Could that be this, if it's intermittent and disappears with a blip of the throttle?
I watch the guages vigillantly, and the temps are all fine, and no CEL's.
Any help is appreciated,
Thanks,
Jeremy

 

It could be a number of things. The first that come to mind are the water pump, alternator bearing, AC clutch, and chipmunks or squirels.

My quess would be squirels because they tend to chatter when they get excited. They might be grey, red, or even black(AKA flying squirels). If they are black be careful that they don't get into the house cause they will keep you up at night with their chattering and running around. The best way to avoid them is to move to someplace that dosen't have trees. But since squirels also like nuts and you have an AUDI it will be hard to get rid of them.

 

Could that noisebe from a timing belt tensioner failing? Heard it once on my p car, the scariest noise I've ever heard.

 

firstly does it do it in P ( tranny in sleep mode ) that's not active to you lol, if it does it only when in D then you have a problem and it needs diagnostic test ( is there any ATF fluid lose round the tranny seals? ) same as looking for an oil leak from the sump gasket

 

So get this!! After having the noise come back on the way home, and not being able to fix it by blipping the throttle, I got worried again. The best way I could describe it was either a throw out bearing or the sound of LOW OIL. But, i figured, the sensor would send a signal if the oil was low, right? NOT THIS TIME! I was down a full quart!!! SO I topped it off, restarted the car and it was still rattling, so now I'm thinking I did permanant damage, but I blipped the throttle and it went away, and hasn;t come back since after several trips and stops and starts of the engine.
So that's the latest.
Dave, since you asked, it did it in Park and Drive in every gear. But it's gone now.
Could it have just been low oil? And if so, could there be any permanant damage if the noise went away and it was only a quart low? And why didn't my low oil light come on???

Thanks again...
Jeremy