Even if I'm driving it fairly easy, without pushing it, whenever I turn the car off I hear a sort of faint hissing noise, it almost sounds like it's coming from the vents. Just a few minutes ago I got home, and sure enough, as soon as I turn the car off, there's an audible hissing noise. I have no idea what it is, or what it could be. Anybody have the same problem as me, or is it fairly harmless? I've assumed thus far that it's nothing major. The car runs perfectly fine, and this hissing isn't affecting anything (yet??) Lemme know what you guys think.

 

Open the hood and have someone listen for the noise and make sure its not coming from the engine bay VS the a/c system.

 

I have something similar happening. Is it a single tone or is it broken up? When I cut my engine off I hear a hissing sound that seems to be coming from the vents infront of the windshield but the sound is broken up like something is building up pressure then pushing a valve open, then closed.

 

It's a flat single tone, then it breaks up somewhat and continues. I'll have someone check it out tomorrow to make sure it's not an engine thing. But now that I have your godly attention, auditech, what could be going wrong if that is the engine?

 

Some type of PCV hose could be clogged up or the PCV valve has been known to make hissing type noises when they get clogged.

 

Is there a DIY method for cleaning the PCV hose/valve? I'm not getting a rough idle or anything; like I said, the car runs absolutely fine until I turn it off, and then it just sounds... almost... relieved. The hissing is almost a continuous sigh that subsides after a few minutes.