It does sorta sound like that, but much fainter. You can barely hear it and it comes from the right rear, unlike the main horn or the honk when the doors are locked.

 

I dont really know what to think. It almost seems like it it is vapor venting. That is what the service techs at the dealer thought also. Since the april recall has something to do with a fuel part (cracking nipple, they say) it may be related to that. I do not know where that recalled part is located though. It does not ever get louder past a certain point. Then as the car cools, or the pressure is released (maybe), it progressivly gets lower and lower until it stops. But it is always the same frequency, which is odd. You would think that if it were some kinda pressure or vapor venting or something, it would not be consistant.

 

Thanks, I will try and get in there with the stethoscope the next time it does it and see if i can tell if its the filter or not.

 

this may sound werid but it sounds like the little security horn in the trunk.. like its malfuntioning or something.. you should disconect it once and see if thats it... its behind the jack kit on the left side of the trunk you have to take the jack out to get to it..... try it once.. thats just what it sounds like...lol i know its weird but its worth a shot... just leave it un hooked for a day

 

OK, I found it, or at least part of it! Today i spent about 20 minutes with the car jacked up going over every inch (that I could) of the right rear of the car. It is defiantly fuel related but I don't think its the filter. I felt the fuel filler neck and it was vibrating a little when the "honking" was happening. I then unscrewed the fuel cap, it mad the vacuum/venting noise as it released pressure and immediately the honking stopped. So,p could it be something so simple as a gas cap or could it be something else? Fuel caps are cheap so I am going to pick one up tomorrow and see if that does the trick.

 

Let us know how it works out.

 

It sounds like a fuel pump that hates you, but seriously fuel pumps heat up after usage, sometimes this causes the overload to partially open, although mine did not honk when hot, it buzzed and made a high pitch whine. It was indeed a failing fuel pump which failed, I thingk that you should have the rollover nipple service and see if that makes any difference. If not pull the backseat and listen to the fuel pump, it is alot easier to hear with the seat out.

 

I had a 2000 A6 2.7T that did the same thing. When it was hot I'd get that little honking noise every 1 or 2 seconds for several minutes after I shut the car off. I was told it was the fuel pump cooling down and relieving built-up pressure. I don't know enough to tell you if that's accurate or possible, but since releasing the pressure from the gas cap made the noise stop, I assumed it was accurate and went with it.