Consistent hum from under hood, no other symptoms in Pontiac Grand Prix

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  #1  
Old 08-01-12, 05:00 PM
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Consistent hum from under hood, no other symptoms in Pontiac Grand Prix

My 2006 Grand Prix began making a humming sound during a recent roadtrip. Incredibly, this happened the day after my service contract expired.
It sounds similar to something rubbing against the tire tread. I have thoroughly examined tires and axles and found nothing out of place.

Some notes on the sound:
- the sound is constant when vehicle is in motion
- it gets louder with increased speed
- while coasting over 25 mph it can be heard clearly over the engine
- pressing the gas/ break have no effect (independent of difference in speed)
- the sound seems to originate under the hood, closer to the driver's side
- it almost sounds like a modified exhaust tip (like on a "ricer")

I have now driven over 250 miles. The sound doesn't seem to have changed much (it may have gotten slightly louder, or I may just be listening harder), and the car is functioning completely normal otherwise.

WTF?
 
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  #2  
Old 08-01-12, 06:37 PM
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I have same in my Silverado for over a year now. Dull humm. Turn music up.
It does sound like it is sucking air into exhaust or something. Yep. Whoooooooooooooooooooooooooooo
 
  #3  
Old 08-01-12, 09:30 PM
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you have a bad wheel bearing, i bet the noise chages or goes away on sharp turns above 25 mph
 
  #4  
Old 08-02-12, 02:44 PM
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no mine. mine is steady, move or not. and comes from behind my driver seat backrest, straight down.
 
  #5  
Old 08-02-12, 03:39 PM
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id say yours (ukrbyk) is bad trans mount. big guess on that
 
  #6  
Old 08-02-12, 04:47 PM
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all mounts are good, I check on them every time I do oil changes. My hummmm does sound like it's air blowing through something. But it's non-relevant to rpms. Faster, slower, moving or not - as far as engine is running, it's same blowing air hummmm.. I got used to it. whooooooooooooo
 
  #7  
Old 08-03-12, 10:35 AM
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the wheel bearing does sound likely. the noise actually gets louder during sharp turns. it is unrelated to rpm but directly related to vehicle speed
 
  #8  
Old 08-03-12, 11:19 AM
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All fluids topped up and all have been refreshed as needed? Any noise when parked and steering wheel turned? Any strange steering behavior? How many miles on the car? Exhaust mounts are ok right? Are you sure it could not still be tire tread noise from a tire going bad? How old are the tires?
 
  #9  
Old 08-04-12, 01:22 PM
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All fluids are good. No noise from the steering wheel or steering issues of any kind.just under 100,000 miles on the car. exhaust mounts look fine as far as i can tell from visual inspection. tires are halfway through their tread life, and i had them rotated after the noise began, which changed nothing.
 
  #10  
Old 08-04-12, 04:43 PM
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You know, if you can hear it without car moving, and with hood open, use something to locate it. Might be something as simple as humming relay.
 
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