My Imac is from the same generation as yours. 2 days ago, I encountered my fans powering at full speed, making loud noises. I was panicked and called up the Apple support hotline. After doing a reset of the Imac as instructed, the fans' speed is back to normal. So far, nothing unusual happen.
Here is the link to do the hard rest, http://support.apple.com/kb/HT3964. Hope this can help you.
I have the same noise as in the video. SMC and PRAM don't touch it. I think this is a physical issue with the fan, not a firmware problem. Speeds aren't an issue for me. The CPU fan is actually running very slow, which I think is why I can hear this. When it speeds up, it becomes somewhat more like what I'd expect.
At this point, I'm going to take it *back* to my Service Center and point them to the video since they can't hear my actual fan in their shop due to the noise levels there.
I know it's the cpu fan instead of the hdd because I've altered the speed of the fan using iStat (I put it right back to where it had been).
This is pretty lame. 2500.00 for a top of the line machine. They can spend the extra 3.00 on a better fan. I'm *very* disappointed.
Yes it's definitely the CPU fan as the noise can be altered by increasing the fan speed using smcFanControl. As you say, SMC and PRAM resetting don't resolve the problem. My iMac now sounds like a tractor at times - in fact, most of the time. It's absolutely fine in all other respects, but this noise is unacceptable.
My problem is that in New Zealand there are no Apple Stores or Genius bars and having paid NZ$5,500 for a pretty much fully loaded iMac, I'm facing the risk of an unsatisfactory repair experience in the hands of a third party Apple Approved Service Provider. Consequently, if any community member has resolved this without returning the iMac to base for repairs I'd be very interested to hear about it and give it a try.
I just know that as soon as the iMac goes in for repair, it will come back with other secondary problems and my high investment will be trashed with the iMac never being the same again.
This is not what I expected from the flagship model from a premium brand ..... so *very* disappointed is a significant under-statement in my case.
So, how many people have experienced this CPU fan noise and can it resolved without a return to base?
There are more YouTube videos of this problem .... from quite a long time ago, so it appears to be a longstanding common problem for which there must be an answer .... hopefully without requiring invasive return to base surgery
Hey, I have the same problem here, i've had a few imacs and they were all pretty silent and would expect the same from a 2011 state of the art $1,800.00 computer ... that's why i bought it. Had to have the HD replaced because of a grinding noise and now the fan is making a whirring noise... i sit at this thing sometimes 10 hrs a day... drives me mad ... took it to apple they say it is normal... $1800.00 for state of the art rubbish.
Same problem, & bought around the same time with the same model.
We went Mac all the way after leaving Christchurch, & really regret the purchases, we got 2.
My iMac does the full noise fan, with adled CPU so you can't do anything intense on it.
I used to be able to cure it with the SMC reset. But this got annoying sometimes having to do it every 20 mins.
I took it back to the shop three times before I finally just started screaming at them. They took it for a few weeks & replaced the motherboard. That cured it for a month, & then it started again, slow at first, but now it is back to pretty much as soon as I turn it on, right before Easter when I wanted to get some serious gaming in.
They blamed everything, the fact I had Windows 7 on it via boot camp, the fact I had non-apple ram I bought from OWC, the fact my apartment was not air-conditioned, then when I told them it was, they then said that air-conditioning had be know to cause issues... that was when I started screaming.
pretty over it at this point, we bought Adobe for Mac, Office 2011, cost us over $17,000 for the 2 iMacs & software. I am now looking to get the thing fixed & sell them & go back to PCs with a Mac mini to just plug into the TV for iTunes & our pics.
I Love my iPads, iPhones & iPod; but my iMac needs to be drop kicked! My wife's one had the DVD rom not reading. It was pretty humiliating taking both iMacs back to the shop within a week, & then being told we would have to leave em there for two weeks as we had not bought them from there & it was our fault for using Apple Store online.
Since, you have had several repairs done on these iMac's under AppleCare, you can request that Apple give you brand-spankin' new iMacs with your specs. If you have to, go right to the top manager at the Apple store.
If each machine has had, at least, three major repairs, then you are entitled to a brand new iMac with identical specs.
Demand that they honor this part of the AppleCare agreement.
Exactly the same problem here. I have an iMac 27 mid 2011. Fan sounds like a hair dryer in my face. I'm a music producer and I can't live like this. If I record near the machine I'm recording fan. SMC and PRAM resets appeared to work at first but now do nothing. I took it to local Apple store, queued up with armies of teenagers holding pink ipods where eventually they tested the hardware and said nothing's out of the ordinary.
So I took it home and managed to speak to a senior Apple tech on the phone. He suggested putting iTunes into safe mode by pressing Alt and Command whilst opening it. This seemed to work for a few days but now the fans on full again yet as I type, the temperature monitor says 42 degrees. THIS IS RUBBISH APPLE!! How about a permanent fix for this? You built the machines, we spent thousands on them. Now tell us what's going on. My iMacs set up directly in front of my window and I'm sorely close to seeing whether it can fly. Some proper help and explanation would be very useful.