Resolved 2011 27" iMac Overheating Issues

[kevinakerberg]

Hi everyone,
I bought a used 2011 27" iMac outfitted with the 3.1GHz i5-2400 processor, 8GB of RAM, the 1GB HD 6970M GPU, and the standard 1TB hard drive back in December of 2016. The machine was very well taken care of and had no issues. It even came with all of the documentation, keyboard and mouse, and original packaging. It's been nothing but awesome since I first got it, even when doing more demanding tasks like video editing. However today I was doing some light school work on it (Google slides in Safari) when it froze, turned itself off, then restarted. Upon restarting it bonged and then showed the boot up screen with pink vertical lines on the display. I panicked because I knew that these machines suffered from graphics card failure, but even though it's not entirely ruled out it's pretty safe to say that it's not a graphics issue. The machine never booted up fully and always restarted, and the one time it did boot up (with no lines or anything marring the display) it was sluggish and slow, and even trying to open system profiler caused it to reboot. The machine is also very hot to the touch and smells like it's burning. To me it seems like it's too hot for normal operation and must turn itself off to save the internals from burning up. So to sum things up I want to know how do I fix the overheating and is that even what's happening? Thanks.

 

[DeltaMac]

If it smells hot, that's not a good way to have it running. I would recommend that a full cleaning, inside and out, is your next step, paying close attention to every cooling air passage that you can find.
But, I would be concerned that it shuts down as quickly as you say, which might NOT be caused by overheating.
Could be a failing hard drive, but you also want to make sure that all 3 fans are running. The fans will ALWAYS run when power is on.

One quick place to check first for a clogged cooling inlet is on the back of your iMac. There is a round vent under the hinge, above the power connector. That might be clogged, easily cleaned by wiping across that vent.
Open up your iMac, and clean it out. It's not too difficult to get inside those older iMacs.
Make sure that all three fans are clean and clear. Check that ALL fans are running when powered on. You can check that easily with any utility that will display the temp sensors and the fan speed.
Finally, if those tips don't help much, you would want to consider replacing the CPU heat sink compound with fresh compound, properly applied.

 

[keysofanxiety]

Upon restarting it bonged and then showed the boot up screen with pink vertical lines on the display... The machine never booted up fully and always restarted, and the one time it did boot up (with no lines or anything marring the display) it was sluggish and slow, and even trying to open system profiler caused it to reboot. The machine is also very hot to the touch and smells like it's burning.

Honestly this does sound like graphics failure. Furthermore if the fans are immediately blasting and it gets very hot within a minute of turning on, it's a lot more than just a bit of dust in the fans (though that certainly could be compounding the problem).

The machine never booted up fully and always restarted, and the one time it did boot up (with no lines or anything marring the display) it was sluggish and slow, and even trying to open system profiler caused it to reboot.

Even if the HDD was colossally corrupted it wouldn't normally cause the system to reboot once it's actually in the OS. Again, sounds like graphics failure. 99.999% certain based on your description.

Do you have an Apple Store local to you? Certainly if the system won't post or boot into the OS it would be best for Apple to assess it.

 

[T'hain Esh Kelch]

I also vote for graphic card failure. It can exhibit in many different ways, but colored lines down the screen is a sure way of diagnosing it as such.

 

[kevinakerberg]

That is what I was assuming, and I think if I try a few more things and the problem still isn't resolved, then I'll take it to my local Apple Store. Thanks to all of you.