Weird noise, is it a fan?

[bazeboiee]

Hi guys, hopefully you can click on this and let me know if this noise from my 21.5" mid 2011 iMac is a fan thing or something more sinister.

https://www.dropbox.com/s/g8r494gthfwfzew/iMac.mp3?dl=0

Thanks in advance.

 

[nambuccaheadsau]

First up is that loud bash two seconds or so from the end part of the noise?

Sounds very much like a fan. Hard drives usually have more of a clicking noise. Hard drive ever been replaced? If so was a heat sensor kit used?

 

[chscag]

It does sound like a fan. Now you have to figure out which one since your 2011 iMac has three fans running. You can probably tell which is the noisy fan by using something like iStat Menus that gives a readout of the RPM for each fan.

 

[bazeboiee]

Ok cool thanks for the update. I think it must be the fan bottom right but I'll double check. Sound is louder over that side and I haven't replaced a thing in it yet except for upgrading the memory.

 

[bazeboiee]

Btw the loud noise at the end isn't part of it, that was me moving around the iMac.

 

[kschendel]

I've heard hard drives with bearing problems make similar noises, but HDD bearing noise is steady, not wavering like that. I'll agree with it being fan noise.