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Discussion Starter #1
So, while poking around under the hood trying to see if I can fix my AC line, I noticed that after I turn my Outlook off, I get this quiet high pitched, vaguely electronic sound followed by a clunk, then it repeats. Sort of 'Wheeeeeeeeeeeeee-katchunk Wheeeeeeeeeeeeee-katchunk'. It sounds like it's coming from up under the base of the windshield, at the firewall. I don't see an obvious source, though.

I also seem to hear the high pitched sound while the engine's running too.

Is this normal and I've just not noticed it before?
 

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Sounds to me like bearings going out and or a motor burning out. Maybe you a/c problem. The kyatchunk at the end would be the compressor slamming to a stop.
 

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Discussion Starter #3
It doesn't sound like a bearing whine, more electric or electronic, and it happens after the engine is off. The compressor is down low, up front and I've pulled the A/C clutch fuse and relay to keep it from cycling on while the system is empty.

There are A/C lines that go into the dash up there, however.
 

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Blower motor?
 

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Discussion Starter #5
Hmmm, I don't think so, the blower shuts off with the key, doesn't it?
 

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I think I hear the same noise and I believe it is normal operation of the vechicle. Immediately after turning off the vehicle I hear a humming noise followed by 1 or 2 katchunks. Like something either in the engine bay or firewall is closing off. In my 2002 Pontiac Grand Prix I was able to isolate the noise and attribute it the vacuum like mechanism exhibited by the PCV valve (it was some type of spring loaded bearing) but on this Acadia by the time I run out to check what is making the "humming-electrical-like-buzzing" noise and "katchunks" and open the hood it is too late and over within a few seconds. I know it is normal because my buddies 2010 and the newer 2012 I had as a loaner for several days all made the same noise after shutting the vehicle off. It is probably a component that is vacuum-related or pressurized with an electrical relay component to it as well. I hope this is the same noise you are describing and hope this helps you out.
 

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I have the same noises on my 2010 Traverse upon shutting off the engine. Someone posted they think it's the high pressure fuel pump which is under the hood near the firewall?
 

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ls973800 said:
I have the same noises on my 2010 Traverse upon shutting off the engine. Someone posted they think it's the high pressure fuel pump which is under the hood near the firewall?
Sounds logical and I think rbarrios might have commented on this on a previous post.
 

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my 2010 does it too.

I describe it as something "Parking" in the rest position.

Ive heard others describe it as a ping pong ball like sound (a heavy one)...

THough Ive never searched for the source.... I will try it one of these days..
 

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rbarrios said:
my 2010 does it too.

I describe it as something "Parking" in the rest position.

Ive heard others describe it as a ping pong ball like sound (a heavy one)...

THough Ive never searched for the source.... I will try it one of these days..
ping pong ball like-ish sound is what I would best describe it as myself :thumb:
 

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Origin of noise @ Shutdown - Transmission Solenoids

Normal noise... per GM Techlink:

Transmission Noise
By techeditor on April 1, 2007 7:34 PM

The owner of a 2007 GMC Acadia or 2007 Saturn Outlook may hear a high pitched buzz or whine noise after the engine is shut off. This buzz or whine noise is coming from the solenoids in the transmission. These solenoids will stay active during the TCM shut down, which will last about ten seconds.

DO NOT make any attempts to repair this concern. This is a normal characteristic of this vehicle.

- Thanks to Ron Erman


http://www.sandyblogs.com/cgi-bin/mt/mt-search.cgi?search=.&IncludeBlogs=3,6,7,10,11,12,14,23,28,29&limit=8&page=393

Be aware, that while this note is for 2007's, the 6T75 transmission design has not changed significantly through MY2012, so this note applies to all Lambda years.
 

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Discussion Starter #13
Thanks all, good to know it's normal.
 

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Re: Origin of noise @ Shutdown - Transmission Solenoids

XRDreamliner said:
Normal noise... per GM Techlink:

Transmission Noise
By techeditor on April 1, 2007 7:34 PM

The owner of a 2007 GMC Acadia or 2007 Saturn Outlook may hear a high pitched buzz or whine noise after the engine is shut off. This buzz or whine noise is coming from the solenoids in the transmission. These solenoids will stay active during the TCM shut down, which will last about ten seconds.

DO NOT make any attempts to repair this concern. This is a normal characteristic of this vehicle.

- Thanks to Ron Erman



http://www.sandyblogs.com/cgi-bin/mt/mt-search.cgi?search=.&IncludeBlogs=3,6,7,10,11,12,14,23,28,29&limit=8&page=393

Be aware, that while this note is for 2007's, the 6T75 transmission design has not changed significantly through MY2012, so this note applies to all Lambda years.
Thank you for sharing that information.

I hope you have a great weekend.

Michelle, GMC Customer Service
 

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Love the topic name though - makes me almost hear it. :thumb:
 

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It was probably 'stolen' from a car care commercial! :eek:
 

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50andretired said:
Sounds more like a pig on an auto insurance commercial ;D
Deliverance? :facepalm:
 

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I suspect the clunking noise your hear, after the engine is turned off, is the StabiliTrak system disengaging. I too hear the high pitch noise and two clunks when I turn the engine off. I figured the high pitch noise was some sort of vacuum, but didn't know the reason for it until XRDreamliner posted the comment. Thanks XRDreamliner for the explanation. Since the StabiliTrak system makes two engaging clunks when I first drive the vehicle and before the vehicle reaches 20 mph I always assumed the clunks I heard after the motor was turned off was the StabiliTrak system disengaging. But that's just an assumption on my part

The high pitched noise you hear while the engine is running might be coming from the Auxiliary Vacuum pump. See this post from rbarrios for more details http://www.acadiaforum.net/index.php?topic=10403.msg171243#msg171243 but this noise would be present only when the engine was cold.
 

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golf2beach said:
Since the StabiliTrak system makes two engaging clunks when I first drive the vehicle and before the vehicle reaches 20 mph I always assumed the clunks I heard after the motor was turned off was the StabiliTrak system disengaging. But that's just an assumption on my part.
The noise you describe is the ABS self-check which occurs around 7-9 mph.
 
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