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So I'm fairly sure it's not the actual CPU cooler making the sound, but there is a loud whirring sound coming from behind it. It started when I rebooted the computer after a power outage. It has made this noise before but it eventually stopped. This has not stopped since last night. What could be the issue and what should I do?

One of the fans is probably on it's way out. For a lot of bearings that are wearing down, the fans will be loud while it's cold, but as soon as the bearings get a little warm the fans will get quiet again as the heat reduces the friction a little bit. As the bearing wear down more, the noise will continue for longer before the bearings "warm up" until friction from worn bearings get hotter and will speed up bearing wear. Eventually, the fan will make a lot of noise and then seize up and die.

You can try to pinpoint where the noise is coming from with something like a tube. Place one end of the tube on your ear, and point the other end of the tube to various locations that might be making the noise. It's best to do this with the computer on while the case is open. Something made of hard plastic works the best like PVC, and about 2-3 inches in diameter. Soft plastic will tend to absorb the high frequency sounds instead of bouncing it inside the tube, making it harder to hear.

I don't have anything like that on hand, but I think I isolated the source. There is a strong airflow coming out of the CPU cooler on its top left side, which is also the source of the sound. Would this be something I would have to send it in to the manufacturer to be fixed?

Stella15 wrote:

I don't have anything like that on hand, but I think I isolated the source. There is a strong airflow coming out of the CPU cooler on its top left side, which is also the source of the sound. Would this be something I would have to send it in to the manufacturer to be fixed?

Hmmm.... now sounds like maybe the Fan RPM controls aren't working correctly because of the strong air flow. I'm assuming it sounds more like a hair dryer than a grinder? Maybe the power outage damaged the control module on the fan and it's causing the CPU fan to run at maximum speed. Depending on your skill level you can try to replace the fan with another fan with a 4 pin connector to see if it's the fan or not. Worst case scenario, the motherboard's fan controls were damaged in which case you might have to use a aftermarket fan controller to tame down the fan speed.

Try blowing the dust out of it with a can of air duster.

1. Stop each fan gently with a finger on the hub to find out which one is making all the noise*.
2. Replace the dud
3. Celebrate with a cold beer.

* - If you can't slow a fan with a finger on the hub, or it looks like a particularly scary fan, turn the machine off, and power it up with a toothpick or similar obstructing the blades. Remove toothpick to see if the noise resumes.

It's probably the bearing is out and you will need to replace it with a new one.