Whirring sound coming from the front end

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#1
Please fill out the following to ask a question.

MAKE: Chevrolet
MODEL: Malibu
YEAR: 2005
MILES: 70,000
ENGINE: 3.5 L V6

About a month ago I noticed that there was a whirring sound coming from under the hood. It sounds very dull and is hard to notice when the car is going under 35 MPH. The whirring will increase and decrease with the speed of the car, so it is very noticeable when driving on the highway as it can be quite loud. I originally though the can could be low on oil, but since adding oil the sound has continued. I have also heard that a fan blade could be bent which would cause the sound, but if the fan is made of plastic, could the blade really bend much without breaking?

I know the details are vague, but I am having a difficult time describing the problem, if there is any more specifi information you need, please let me know. I appreciate any feedback I can get.

P.S. The exhaust system was rotted and was just replaced today. I hoped that maybe the exhaust was the root of the problem and the replacement would solve my issue, but that is not the case.
 
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#2
Can you make the noise by reving the engine while parked? Or does the car have to be moving?
 

nickb2

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#3
If the sound increases and decreases with speed of car, I would focus more on bearings than the engine. So as Jack asked, do you hear it hood open, revving, idling, or just when in motion at a certain speed?

Cuz this sounds like a front wheel bearing more than anything else. Rarely have I seen a differential bearing go out on these trannys.
 

nickb2

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#4
When an engine is in gear and moving, most engine noises will not be associated to the speed the car is driving at, but more at which RPM it is revving on load or floating.

Where as a front wheel drive car will have differential bearings and front wheel hub bearings that will sound off at a certain speed. Try driving the car when it starts to whir and sharp end the car left to right to see if the sound changes. Post back results.
 
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#5
Thank you for the quick replies. When the car is in park and I rev the engine, the sound is not present, it is only present when the car is moving.

Nick, I will test out your recommendation later today and post with the results.
 
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#6
After you do Nick's test, you can also put one front wheel up at a time with a good jack stand under the frame and take it up to speed to see if the noise is on one side or the other or the same on both sides.
 

JP

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#7
Another way to check the wheel bearings is jack up the front end, car in neutral, and feel the spring while someone turns the tire. If the bearing is bad it may vibrate on that side. Not a 100% diagnostic trick, but someone here on the BAT forums recommended it and it worked for me at least 2 or three times.
 

cw41

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#8
have you checked your tiresz?? tires can make a hell of a lot of noise expecially if one is going bad. just my $.02 but i would rule the tires out for noise go get them roadforce balance meaning they can put a load the tires on the balance machine to check for bent rim, bad tire out of balance, etc.