I have a 2005 AWD Vibe that is making a sighing (almost hissing) sound when I turn the engine off. I believe the sound is there when its running, but its really only noticeable when the engine turns off. It may be located towards the top end of the engine, and using a mechanics stethoscope (I'm a newbie so this is my first time using one) it seems I can hear the sound when listening directly to the air intake. I tried other components to see if it was a pulley and I could not hear it, nor could I hear it when I listened to the bottom internals or the valve cover. Does this sound familiar? Is this normal and I just haven't noticed before? For the most part the car drives well, though it seems to not start as strongly as it once did. I replaced the plugs this weekend because they were long overdue and they were well worn (gap was over 2x what it should have been).
My car goes to AAMCO next week for a tranny related issue, so they said they will take a look. In the mean time though if its something I can identify and fix myself I'd rather do that. I will post a video of this issue. There may be some squeaking in the video that is related to my flex plate (getting replaced next week) but the video shows start up and then turning off. When the car turns off its the last sound you can hear.
Possible issues: air intake manifold, maybe a valve issue? Perhaps a bearing issue?
https://youtu.be/WSGJj1oYtg0