I have a 2003 996 C2 cab with manual trans and 17K miles. Sometimes while sitting at idle with the car in neutral, I hear a howling sound which appears to come from somewhere behind the gas filler door compartment. When I open the gas filler door, it REALLY sounds like it is coming from right behind it. I tried loosening/tightening the gas cap and that doesn't help at all. If I give it a little gas it goes away and sometimes the noise stops suddenly on its own...any thoughts? I can't remember if it only happens when it is cold or not.
Thanks,
Allan

 

I'm no specialist on these cars but I do know the evap canister is behind that area and there may be vacuum tubes associated with it. By how you describedthe noise it sounds like a vacuum leak at that area. Pull the front wheel and wheel house and start it up on jack stands to see if you can locate the leak.

 

Excellent...thanks for the info. It was so much easier to crawl under my Jeep and check things out. I'll put my warranty to use and have them check it out while I get my oil leak fixed. Thanks again...I like to know what the problem may be before taking a vehicle in....