I've had the car for about a year now and just tonight I noticed that there was a noise coming from the rear of the car. It sounded like a small air pump (low pitch - not a whine like a fuel pump). It continued for 2-3 minutes, after I shut the engine down, then stopped. I figured it might be some kind of fuel system vapor purge, but I can't find anything about such a system in the shop manuals (at least not one involving a pump). No mention of this in the owner's manual, couldn't find anything in searching this forum...

Anyone familiar with this noise and what it might be? If it's normal, I'm surprised I haven't noticed it before now...

 

car does an evap system pressure/leak test after the car is shut off