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iMac 5K late 2014 overheating

Cruciarius

Cruciarius

macrumors regular
Original poster
Aug 18, 2013
109
17
Massachusetts
I've had this iMac since it's release. Been running great, until a while back it kept forcing itself to sleep and even shutdown sometimes, while in the middle of something. Found out the cause was overheating. Brought it to Apple and they replaced the screen, logic board, redid the heat sync, and I don't know what else. After that, it ran fine. Until recently, just after my Apple Care ran out of course (was covered before). Back to over heating issues after less than a year of the repairs.

Currently not running too much, Twitterrific, Discord, Safari (this window & 2 Twitch streams) and the GPU is sitting around 170-180º. Seems each Twitch stream I open adds another 5-10º on top of that. If I open a game, it'll jump 30-50º, which may be normal for all I know, but I never think of watching the temps until an issue starts happening. When the iMac gets to be around 200-250º it goes to sleep/shuts down, which I think is normal.

Problem is, I'm not too keen on trying to repair this myself by opening it up and redoing the heat sync. Would Apple charge a lot for just that? I know a logic board replacement and other stuff they did before would have cost me a lot, if it hadn't been under warranty. Was planning to wait until next year to replace this iMac, but with more than half the year to go and unsure when new Mac models will be out next year, I don't know if I can wait that long with this one in the current condition.

I've seen a few people suggesting sticking fans on the back of the iMac to help. Does that really help? A fan blowing against the body of the iMac, not into the vents, doesn't seem like it would help at all. Maybe down the temp 1-2 degrees, if anything. If I'm wrong and someone actually does have good results, what fan is used to do this?

Also, a more minor issue I have that started after Apple replaced the screen. The image retention/burn started AFTER they changed the screen. I should have brought it back in to have that issue fixed ASAP, but I was very busy with work & happy that they did fix the overheating issue, even if just temporary, until now. Now it's not under warranty though, so I don't think they'd fix that issue, although caused by them months ago.

Specs:
iMac 5K 27-inch late 2014
4 GHz i7
32 GB 1600 MHz DDR3 RAM
AMD Radeon R9 M295X 4096 MB
 
The app iStat lets you monitor a plethora of sensors, and set fan speed rules for your machine. Here's a glimpse of what sensors it can report on. I have chosen to display values in Celsius, but you can use Fahrenheit, if you must.

It might help you understand which sensors are being triggered, and whether it's a GPU, CPU, or other issue.

I use a i5 m290x machine, so temperatures are far less of a concern.
Screen Shot 75.png
 
Already use that software. The temps I mentioned above is the "GPU Die."

I can ramp up the fan speed to max out at 2,700 RPM, but that doesn't help it very much. Though I'm sure it does, but even just 1 or 2 Twitch streams open and a low system spec game, like Final Fantasy XIV will cause an overheating shutdown.
 
Yesterday I tried to have barely any apps open for a while. GPU sat around 160 degrees most of the day. Then I tried to play a game. Nothing too graphic intensive. Final Fantasy XIV. GPU spiked to over 200 degrees real quick.

Still wanting a solution to try to post pone replacing this iMac until next year. Will a small fan aimed at the back of it really help? Should it be angled into the vents or just the general back of the case?
 
I've done those steps already. Didn't make a difference for me. I'll try again tonight (at work currently), but don't expect it to make a difference. Did this the 1st time I had this issue as well, but it didn't help then either. Even the Apple team tried it, when I went to have it looked at.

How to reset the SMC on Mac desktop computers
  1. Choose Apple menu > Shut Down.
  2. After your Mac shuts down, unplug the power cord.
  3. Wait 15 seconds.
  4. Plug the power cord back in.
  5. Wait 5 seconds, then press the power button again to turn on your Mac.

Resetting NVRAM
  1. Shut down your Mac.
  2. Locate the following keys on the keyboard: Command (⌘), Option, P, and R.
  3. Turn on your Mac.
  4. Press and hold the Command-Option-P-R keys immediately after you hear the startup sound.
  5. Hold these keys until the computer restarts and you hear the startup sound for a second time.
Posting those here for myself, so I have them in 1 place tonight.

With the SMC rest, will it matter if it's exactly 15 seconds? What If I waited say 20-30 seconds?
 
Not sure, 15 sec is probably the time it takes for a capacitor to discharge. More time beyond 15 seconds makes no difference.
 
i had this same issue with my late 2014 iMac. As it was out of warranty and proximity to a repairer/apple i decided to buy a new one :(
 
This type of overheating usually means the thermal compound between heatsink and chip is not applied correctly. Abnormal temps usually indicate a failing fan or incorrect installation of heatsink. I have experienced bad chips too, intel CPUs sometimes have bad thermal performance on their own.

Take it to Apple repair centre and ask them to redo the heatsink with new thermal compound.

Also does your fan spin up. Even on 2700 RPM it's not going to flow air as fast as on normal cpu towers.

Imagine your iMac having same fan as in Macbook Pro or PS4 slim so ambient temps are very important.

PS: CPU core temps will always be high than proximity. As those sensors are inside the die while others are outside the cpu. I don't know why Apple has set the CPU voltage so high (up to 1.8v) in idle. That i5 should be stable at around 1.3v. Unfortunately we cannot modify that.
 
jerwin said:
The app iStat lets you monitor a plethora of sensors, and set fan speed rules for your machine. Here's a glimpse of what sensors it can report on. I have chosen to display values in Celsius, but you can use Fahrenheit, if you must.

It might help you understand which sensors are being triggered, and whether it's a GPU, CPU, or other issue.

I use a i5 m290x machine, so temperatures are far less of a concern.
Click to expand...

What app is that exactly? Looks like there are a few in the App Store. Is it iStat Menus?
 
I have read that the SMC reset should have the power-button depressed while you wait the 15 seconds.

Also, on the PRAM reset, I usually cycle it through 2 or 3 chimes before releasing the keys to let it boot normally.
 
Has it been getting progressively worse?

You might have dust buildup. Apple's design sticky tape design is stupid.
 
Sorry for the delayed in a response after resetting the SMC and NVRAM.

Currently have not much open, but this does include 2 Twitch streams in Safari. With those 2 streams, Discord, and Twitterrific, the GPU temp is currently at 200-210º. If I open OBS Studio, it jumps to 230º and instantly forces sleep. The 200-210º is actually higher than usual. I've had 5 streams open + the other software and been under 200º just fine.

As fas as dust goes, I kind of doubt that would be the cause. As I said before, I did have this issue before while under warranty. They took it apart and replaced parts. I imagine they would have cleaned out dust when they did that. It's only been a few months since then. I'm sure some dust might be in there, but prior to the original overheating repair, I had never taken the iMac apart. Have had this since it came out. Being a late 2014 model, that's a few years worth of dust vs a couple months after it was taken apart and repaired until now.
 
Having repaired my own iMacs, do not even think about doing it until you have all of tools and supplies needed. That said, it isn’t as hard as it seems if you can follow directions. I think a good cleaning might help
 
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