iMac 2012 strange fan noises only at startup

[lanata]

Hello,
I have an iMac 21.5" 2.7 Ghz since April, and in the last two weeks when I turn it on, you can hear the fans going at full speed for a couple of seconds and then quiet down. And when you're using it normally (let's say with Chrome and Photoshop), the noise comes back for a few seconds and quiet down again.
I don't know what's going on, I searched the Apple's knowledge base and found something about fan noises but none relatively similar with my issue.
Thanks in advance for any help.

 

[wrldwzrd89]

I've had this odd issue with my Rev. D (2008) iMac, but not my 2012. I'm not completely sure what causes it either. What I do know is that issues of this sort can be caused by foreign material inside the cooling system - say, dust particles, but that doesn't appear to be the cause of my issue.

 

[lanata]

Thanks for the comment. Let's see if somebody else is on the same boat.

 

[lanata]

After installing some AppStore updates, I think the noise stopped.