Gas tank area noise back and different...
 

Now a steady muffled sound like a distant horn. Stops when gas cap is removed or extended period of time passes. My opinion centers on the gas cap. Round two in 1020 miles to call dealer :-(

Re: Gas tank area noise back and different...
 

Here in Illinois our cars gas caps are tested during the emmisions testing, so I guess one can go bad.

Re: Gas tank area noise back and different...
 

It sounds like some sort of "breathing" or vapor recovery system problem to me. Your smart to start off with the gas cap. It is the simplest part and it is vented. Have you experienced any fuel flow problems (i.e. - pressure building to the point that the fuel pump cant overcome it with resulting engine stumbling)?

Re: Gas tank area noise back and different...
 

It is probably your gas cap. Fuel injetion systems use a pressurized gas cap. The fuel system is designed to run with aprox 50 lbs + - of fuel pressure. Next time you go to the gas station notice the sound of pressure bleeding off when you open the cap. Pressure is crucial! Your cap is probably defective and bleeding off pressure. Think of it as a giant whoopie cushion and thats the sound you are hearing. I have seen this before. BAD10

Re: Gas tank area noise back and different...
 

Have you tried filling up at a different station?
As crazy as it sounds,my BMW would not accept gas from one particular station.

Not yet, but when I opened the cap yesterday there was quite a bit of pressure built up.

I had this exact same noise in my BMW 325is
 

It was exactly as you described. It was eventually fixed with a new cap and neck. Please update if you have time with your resolution. TIA.

Brian

Re: Gas tank area noise back and different...
 

I have the same problem with my 2.7T. My wife describe the sound as moaning. In my case, I think it is temperature related. When I drove into work today, it was 45 degrees and there was no noise. When the weather is warmer, it will make the sound. The sound goes away after some time.

I not sure whether this is normal condition or whether the car needs to be taken in for service.

Re: Gas tank area noise back and different...
 

Steve...yup, thats the exact noise that I'm getting. Didn't drive mine over the weekend though. Will check it tonight when I get home. You say this is happening only when the tank is full?

No, it happened yesterday with only about 2/3 of a tank.
 

I am assuming you're going to call the dealer, as well. Brian, hope you had a nice weekend and good to hear from you.