iMac 2011 27" loud fan speed/noise

[Wakkawoo]

Hello,

Ever since i bought my new iMac 27" i7 3,4 Ghz back in May 2011 i'm having problems with high fan speeds and loud fan noises. I've been investigating this problem and it seems that the fans come on very loud when the average temperature exceeds about 50 ˚C and they don't turn off, unless i turn off my computer (Sleep Mode doesn't work, they will turn off, but turn back on full speed once i turn my Mac back on).

I've installed iStat to monitor temperatures and fan speed. When my Mac has a "fan attack" my Optical Drive fan goes up to 3600 rpm and my CPU fan goes up to 4000 rpm. My HD fan stays normal at around 1100 rpm. The temperature lowers, but the fans don't turn off. And I tell you 4000 rpm is almost as loud as a vacuum cleaner, especially when you're sitting right in front of it.

The other weird thing is that when having such a "fan attack" my overall Geekbench benchmark score is only 6000, but its around 12500 when my fans are behaving normal. So it seems that my mac gets into some sort of safe mode or something like that.

I'm able to "avoid" the problem by using iStat Menus and boosting my fans to blow at around 2000 rpm all the time so the average temperature of my Mac never gets above 50 ˚C, but this isn't an ideal situation as you can imagine, because that is still pretty loud and just not normal!

I have called Apple about my problem, but they told me i had to format my HD and do a clean install of OS X, but i'd rather not because i'm pretty sure it's a hardware problem. I bet there is something wrong with one of the temperature sensors.

Attached you'll find some evidence. Does anyone know what the problem might be and how i could fix it without reinstalling my Mac??

I hope you guys can help me out, because it's driving me crazy

Thanks!

----------
System Information
Operating System
Mac OS X 10.6.8 (Build 10K549)
Model
iMac (27-inch Mid 2011)
Motherboard
Apple Inc. Mac-942B59F58194171B iMac12,2
Processor
Intel Core i7-2600 @ 3.40 GHz
1 Processor, 4 Cores, 8 Threads
Processor ID
GenuineIntel Family 6 Model 42 Stepping 7
L1 Instruction Cache
32.0 KB x 4
L1 Data Cache
32.0 KB x 4
L2 Cache
256 KB x 4
L3 Cache
8.00 MB
Memory
4.00 GB 1333 MHz DDR3
BIOS
Apple Inc. IM121.88Z.0047.B0A.1104221555

 

[alust2013]

I'd try the backup, then a format/reinstall first. There is a small chance that is a hardware issue, but it sounds more like software to me

 

[Spike88]

Perhaps SMC reset might help.

re: http://support.apple.com/kb/ht3964

.

 

[Wakkawoo]

Thanks for your replies. I've already tried a SMC reset a couple of times, and it doesn't help

 

[Spike88]

Sounds like an internal H/W problem. Probably a heat sensor or some other H/W problem.

Possible fixes?

A - Return to Apple Store and being under 1 year old, get them to fix it. They might take for a few days to re-format and re-install from scratch. If a H/W problem (based on their special testing tools), they'll probably open the box up. Probably won't get the box back from 5-7 days. Possibly longer.

B - Download a 3rd party FAN control software (as a trial) and see if that works. For example: http://www.macupdate.com/app/mac/39220/hdd-fan-control Download and try for 1 full hour. If this software fixes the fan speed problem, then buy the software. Based on the comments within its post, it appears this 3rd party software can be used if heat sensors are screwed up. And, its helped many others with their fan speed problems.

If wondering, I use 3rd party FAN Software program in my iMac. Not this specific program but a different program. With fan control software, one can control the fan speed themselves. Glad I use fan control software in my iMac.

Hope this helps...

.

 

[Geezai]

Life time pc user now onto a 27 inch iMac model no A1312.

My wife wanted a Mac. I'm not sure if mine is having the same issue but it is making a constant whirring, like a really loud white noise. It's like the white noise from a set of speakers with no music running but you know the volume is set high.
I thought it really stupid that they would bother putting the hardware above the table when the thing makes so much damn noise. The weird thing is if you pick it up the noise disappears.
Applying pressure up into the base makes it quieter, and once all the weight is off, the thing is silent and how I would hope it should operate like. If somebody would just lift it off the table for me when using it, then all is well.
We're hours away from any apple genius store. The authorized techs in town said he has never seen anything like it in 20 years. Not sure if he is pulling my leg or trying to hide the fact there are heaps of trouble with macs. We are adamant that we want a new one and not a repair.
I think the tech people said they might be able to fix it but at $100 hr they are quoting a possible $1000 bill for apple. Hopefully we will get a newbie. Not impressed with my so called apple experience yet.
The machine has the western digital 1tb hard drive wdc wd1001 fals-403aao. Might be a good one to pick up refurbished as it is otherwise fine apart from the drone that actually gives my wife a head ache and she can't use it. Fan is only 1149 for od and 1099 for hard drive and CPU fan 938.
Any clues to what is going on and what I need to do to deal with apple?

 

[Noisy]

Apple imac 2011 hdd noise - unacceptable for money paid

Your prpblem is because of that WD HDD and you are definitely not alone with this problem, I saw similar problems. I have Hitachi 2 TB HDD and it also creates a recognizable whirring constantky the mac is working. that's just not acceptable for the money we've paid. they have replaced the HDD for free but without any changes. The HDD models Apple puts inside their very expensivr iMacs are cheapest on thr market. WTF, WTF!!! I feel really robbed.
The worst thing it's very hard to install your own HDD even for money cause they are proprietary in 2011 iMacs. You cannot even buy a more quiet HDD from Apple!!!!!!
Currently in 2011 only 512 GB WD seems to be quiet. Seagate 1Tb seems to be OK for white noise but people claim it makes grumbling sounds. wtf apple there are lots of silent modles on the market, stop to sell that crap inside!!! I and many other users are ripped off for the money we paid!!! I require A SATISFACTION!!

 

[Shubes]

Thanks for the tip!

Spike88, just a note of thanks for the tip on the third-party fan-control software.

My fan had already started its upward whine (one out of countless times, only this time I was sitting in front of the iMac, instead of asleep at 3:00 in the morning), which prompted me to do a quick Google on the subject. I found this thread, and your suggestion; downloaded and installed the software, and the fan IMMEDIATELY slowed down. I like the interface - even for the one-hour trial version - that allows me to control when and how fast the fans run. And the fact that my iMac is silent now is priceless.

Thanks again for the tip.