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Discussion Starter #1 (Edited)
The car is a 2009 Cobalt LT Sedan. It recently just started making a loud whining sound, very similar to the sound of a failing power steering pump. The sound is coming from the top end, near the timing chain and cam gear area. It does not do this on cold starts. It only starts once the car is warmed up and driven for a couple minutes and only at idle speed (also coasting at idle speed). If you give it the slightest bit of throttle the noise goes away completely. I have a video of it but the forum won't let me upload it in MP4 format.

No codes are being triggered and it seems to run just fine. But it is parked for now so it doesn't potentially cause a larger issue.

Any ideas or suggestions?
 

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Take the serpentine belt off and then start the engine and see if the noise goes away. If it does then it’s one of the accessory pulleys. If the noise continues with the belt off, it’s most likely the water bump/balance shaft chain needing replacement.
 

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Discussion Starter #4
I have already taken the belt off to eliminate the accessories.

If it were a balance shaft/water pump issue would it create noise up high. I have put a stethoscope to it and its clearly coming from the head/cam gear area.


Also trying to understand why it would only make the noise once it is fully warmed and only at idle
 

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Take the valve cover off and inspect the timing chain. Timing chains normally make a rattling or slapping noise. Yours is a high pitch sound which on these engines typically happens when the balance shaft/water pump chain gets overly tight.
The stethoscope will pick up any noise coming from the timing chain front cover.
 

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To me, I hear a bad bearing. I recently had a Quad 4 come in the with same sound. It was a water pump. Sounded exactly the same and resonated up through the valve cover. Listen to the water pump. If you’ve got the know how to do the timing and balance chains, and don’t mind spending the money, go ahead and swap them and the components out at this time. You say you’ve eliminated the accessor drive belt as a potential issue. I don’t think there’s really any other items that have bearings in this area that’ll make this noise unless the balance shaft chain has idler sprockets. I can’t remember.
 
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