Car exhales after shutdown?

[InvalidUserID]

My 3.8L lets out a sound that, best described, sounds like an exhale after I shut it down. It sounds like it is coming from engine, but not near the aftermarket CAI as I had suspected.

And no "the engine is tired" comments! =)

 

[onion]

Maybe it's just relieved.

 

[Familyguy]

Or perhaps there is enough carbon build-up on top of the pistons to retain enough heat for it to diesel for a stroke or two before it konks out.

 

[Steve S]

It is because you live in the Bay Area.

 

[BuickGN]

My TL does it with the factory airbox though it's much more noticable on the ones with a CAI.

 

[InvalidUserID]

Originally Posted By: Familyguy
Or perhaps there is enough carbon build-up on top of the pistons to retain enough heat for it to diesel for a stroke or two before it konks out.


Over the past 9 years I've had this car, I've only run Chevron and have done the fuel system cleaner annually.

Carbon still a possibility?

 

[c3po]

Originally Posted By: InvalidUserID
Originally Posted By: Familyguy
Or perhaps there is enough carbon build-up on top of the pistons to retain enough heat for it to diesel for a stroke or two before it konks out.


Over the past 9 years I've had this car, I've only run Chevron and have done the fuel system cleaner annually.

Carbon still a possibility?


Doubtful!

 

[mechtech2]

It should be easy to determine where the noise is emanating from.
Have someone turn the engine off while you are under the hood a few times.
Probably pressure past the rings, or maybe a valve.
Engines often stop at the same place.
Maybe even the AC.

 

[97f150]

More than likely the AC system relieving pressure. Is the noise like a slow exhale? If so next time you shut the car down turn the AC off and see if it turns into one big fast exhale.

 

[InvalidUserID]

Originally Posted By: 97f150
More than likely the AC system relieving pressure. Is the noise like a slow exhale? If so next time you shut the car down turn the AC off and see if it turns into one big fast exhale.


The noise happens even when the AC isn't used. The noise itself is rather quick, two seconds max.

 

[Kestas]

Does the engine turn with the noise?

 

[brianl703]

Does the vehicle in question have electronic throttle control? You might be hearing the motor in the throttle actuator--it's fed an AC signal and does make noise that you normally cannot hear because of the much noisier engine.

 

[mechtech2]

Also may be a vacuum leak to a reservoir. Maybe even the brake booster.