Question My top case fan sounds as if it wants to explode ?

[MissyMagnificent]

Okay, it sounds very dramatic, but it really is dramatic. Let me explain. My PC has a total of four fans, one at the back, one connected to the motherboard and three case fans a the front. Every now and then, when I turn on my PC, the top case fan starts spinning slowly and erratically and makes a very loud noise. Like a motor or something really disturbing, I don't know, it just sounds awful. (It's only ever the top case fan, the others are perfectly fine) When this happens I quickly turn my PC off, wait a few seconds and turn it back on and then everything is fine.

Please someone explain to me why the heck this problem is and how I can fix it! Will my PC really explode at some point?! (I don't really belive that.. but this noise can not be good in any way) I would be so greatful for any kind of help here!

 

[zinkles]

Fan noises are usually not something that serious, and it can be due to a number of reasons. Since its a mechanical part, its prone to failure.

Most of the time, it touches the surrounding components or itself and makes sounds in the process, and perhaps turning it off and on moved it by a bit that the sound goes away?

A recording of the sound can help us identify it though..

 

[MissyMagnificent]

Thank you! Unfortunately the noise is very unpredictable, I never know when it will start next time... It will only happen when I turn the PC on, for example in the morning or sometimes when I have switched it to sleep mode and turn it back on again. It is very inconsistent... the next time it happens I'll make sure to record it! But your answer was super helpful already to just make sense of why that might be

 

[lordmogul]

The fan might simply on the way out.
Especially when it's a grinding noise.
And yes, knowing how it sounds would help identifying what it is.

 

[bill001g]

Most people have more fans in their case than they actually need. If your top fan were to totally fail it is likely you would not even notice...at least software wise. Maybe if you have some fancy fan control software the other fans might run slightly faster to compensate for a failed fan.

Unless it is some fan with fancy led, fans are extremely cheap. If it concerns you just buy a new one and replace it. If it makes too much noise you can also just disconnect it. Really the only fan that you really have to be concern about making noise is the one on the cpu cooler.

 

[Cellie]

Thank you! Unfortunately the noise is very unpredictable, I never know when it will start next time... It will only happen when I turn the PC on, for example in the morning or sometimes when I have switched it to sleep mode and turn it back on again. It is very inconsistent... the next time it happens I'll make sure to record it! But your answer was super helpful already to just make sense of why that might be

It's probably only producing the noise at a specific RPM. If you want to reproduce it you'll need to monitor the RPM, take note of the speed when it happens then use a software like Fan Control to place the fan in that rotation.

 

[Paperdoc]

The bearings on that fan may be wearing out. This is the typical sequence of that issue.

First indication is that the fan makes an odd noise for a minute or so when first started up from a long no-use period so it is cold. Then it goes quiet and stays that way while you use. If you reboot it still is quiet. If you shut down for a long while so it cools off, the noise comes back at start-up for a short while.

Over some months the period of initial noise get longer. You MAY notice it running slowly while it is noisy. Eventually it becomes almost always noisy.

The last stage is that the fan seizes up completely and will not run. The time for all this to progress may be a year or more.

As a fan runs normally, the fan shaft and the sleeve bearing it runs in wear, and the small gap between then gets larger. At some point that allows the shaft to "rattle" loosely in the bearing sleeve. Now, this effect is altered by temperature, because the shaft and the bearing metals expand at different rates. That is why the noise stops when the fan warms up from use. But the wearing process continues, so the issue gets worse until the damage is so bad the friction in the bearing just stops the fan.

There is no "Cure" for this. The only solution is to replace the fan. IF this pattern sounds like what you experience, you have about a year to plan when to do the replacement.

 

[Cellie]

@Paperdoc Out of curiosity, is audibly rattling only at certain speeds a characteristic of a specific type of bearing or is it common?

Usually I don't stick with fans long enough they start to wear this way, but I had a 120mm fan acting similarly to the OPs, except the rattle when trigged was very subtle but annoying.

 

[Paperdoc]

Cellie, yes, that can happen. It happens that, decades ago, I did research in the way molecules absorb energy from microwaves. The root of that process is the normal natural rate of rotation of molecules. If you expose them to an electromagnetic wave of a very similar frequency they absorb energy from the field to gain energy. That is how microwave ovens work. Oddly, that made me realize a bit later that the same principle applies for LOADS of things in life. All mechanical systems have a natural resonant frequency so that, IF they are operating just at that rate, they will shake a LOT more. I've seen this in heavy industrial machinery, in unbalanced car tires, even in a mug of coffee. If you walk holding a mug of coffee at the wrong pace it will slosh over the rim but if you change your pace either faster OR slower, the sloshing will get much less. Same principle for a rotating motor shaft in a loose sleeve bearing.

 

[MissyMagnificent]

The bearings on that fan may be wearing out. This is the typical sequence of that issue.

First indication is that the fan makes an odd noise for a minute or so when first started up from a long no-use period so it is cold. Then it goes quiet and stays that way while you use. If you reboot it still is quiet. If you shut down for a long while so it cools off, the noise comes back at start-up for a short while.

Over some months the period of initial noise get longer. You MAY notice it running slowly while it is noisy. Eventually it becomes almost always noisy.

The last stage is that the fan seizes up completely and will not run. The time for all this to progress may be a year or more.

As a fan runs normally, the fan shaft and the sleeve bearing it runs in wear, and the small gap between then gets larger. At some point that allows the shaft to "rattle" loosely in the bearing sleeve. Now, this effect is altered by temperature, because the shaft and the bearing metals expand at different rates. That is why the noise stops when the fan warms up from use. But the wearing process continues, so the issue gets worse until the damage is so bad the friction in the bearing just stops the fan.

There is no "Cure" for this. The only solution is to replace the fan. IF this pattern sounds like what you experience, you have about a year to plan when to do the replacement.

That's exactly the problem I'm having! Thank you for your explanation and your help!

 

[Paperdoc]

You're welcome, and thanks for Solution.