Low volume mystery noise, when ignition off, coming from rear PS tire

[Elvis 3.0]

When I parked my X in the garage last week I heard a low volume mystery noise coming from the outside wheel well on the rear passenger's side. It sounded like a very low fan, or hum. I opened the back hatch and check the rear compartment above the wheel on the inside to double check that it wasn't coming from there. You could still slightly hear it inside, but it was certainly more pronounced outside. It lasted for at least a minute while I was there, and then I walked into my house only to return much later and it had ceased.

Any ideas what it is/was

[div2]

I've noticed the same noise every now and then on my 2004 X3. I never had it looked into but my guess is it has something to do with the fuel system venting or relieving pressure. I wouldn't sweat it- my truck has over 165k on the clock and no problems(from that corner of the sled, anyway)

[Elvis 3.0]

i was away for the weekend or would have replied earlier.

appreciate the input

[div2]

No problem- glad to help!