iMac keeps freezing - very high temp readings

[AlexGraphicD]

I decided to give it a go and post the issue that is plaguing my computer for quite some time now and it is beyond annoying. It will freeze up just like that and occasionally it will restart by itself. I also notice high temp readings and I don't understand why is that, even when I have apps open at the same time like Mail, finder and safari with multiple tabs that's when it happens mostly. I have iStat installed and I notice that CPU reaches temps up to 190° F even when I'm just browsing in Safari and having multiple finder tabs open. Is the high temp the reason for these random freezings or it could be an indication of a faulty hard drive?

Specs:

Catalina 10.15.4
Retina 5K, 27-inch, Late 2015
3.3 GHz Quad-Core Intel Core i5
24 GB 1867 MHz DDR3
AMD Radeon R9 M395 2 GB

I was kinda hoping the issue would go away, I tried all the common solutions that I found online like SCM and PRAM reset but the issue keeps coming back.

 

[chscag]

What troubleshooting have you done? Boot to Recovery and run First Aid on your hard drive, fusion drive, or SSD (whichever you have). Random freezing could be a hardware problem or even a software problem. Sometimes bad memory can cause it but less likely on a machine that has been around for awhile. Try booting to Safe Mode to see if the freezing occurs there also.

 

[casperes1996]

When it restarts on its own, I assume you get a log of the kernel panic; what does it say is responsible for it?

I recommend backing up important information and just reinstalling macOS. It’s a fast and easy way to almost entirely rule out software issues

 

[AlexGraphicD]

What troubleshooting have you done? Boot to Recovery and run First Aid on your hard drive, fusion drive, or SSD (whichever you have). Random freezing could be a hardware problem or even a software problem. Sometimes bad memory can cause it but less likely on a machine that has been around for awhile. Try booting to Safe Mode to see if the freezing occurs there also.

I think sometime ago I run the Apple Diagnostics but it didn't find any error. Haven't tried Safe Mode though, cause I don't know how long it might take for the issue to come up, but I'll give it a try this time, I want to try everything.

When it restarts on its own, I assume you get a log of the kernel panic; what does it say is responsible for it?

I recommend backing up important information and just reinstalling macOS. It’s a fast and easy way to almost entirely rule out software issues

I'm sorry but how can I locate the kernel panic log for that specific issue and I will post it here. I see a "system.log." file from the Console app, is that the one?

 

[AlexGraphicD]

What troubleshooting have you done? Boot to Recovery and run First Aid on your hard drive, fusion drive, or SSD (whichever you have). Random freezing could be a hardware problem or even a software problem. Sometimes bad memory can cause it but less likely on a machine that has been around for awhile. Try booting to Safe Mode to see if the freezing occurs there also.

UPDATE:
Okay I tried to boot in Safe Mode twice and the issue came up immediately, first time it froze up when I logged in the computer and second time when I was in the login window trying to enter my password, it stopped responding and restarted after a few seconds.

If I do a clean install, does that mean that I can restore everything as it was before from my Time Machine backup or do I have to install all of my apps and settings all over again? Sorry, I also didn't mention on the thread, I have installed Catalina 10.15.4.

 

[casperes1996]

I'm sorry but how can I locate the kernel panic log for that specific issue and I will post it here. I see a "system.log." file from the Console app, is that the one?

They are here:
/Library/Logs/DiagnosticReports

In Console you should also be able to dig to that folder from the sidebar.

There should be something from roughly the time the computer restarted on its own, assuming it registered as a kernel panic

 

[Juicy Box]

I think sometime ago I run the Apple Diagnostics but it didn't find any error.

In my experience, Apple's HW diagnostic test gives false negatives often.

 

[CooperBox]

I'm just wondering what sort of environment you are using it in, i.e. dusty, sandy, hairy etc. When I opened up my 2010 iMac 27" to install a Samsung SSD, I was horrified to find both fans heavily clogged, which looked far worse on the fan hot air exit side when I removed them for cleaning - and I always thought I was in a relatively dust-free home.
Must confess I never experienced the iMac freezing, and never monitored the temps before or after cleaning, but with the clogged debris found in the fans it's amazing I never experienced what you're seeing. That could possibly explain your overheating.

 

[AlexGraphicD]

I'm just wondering what sort of environment you are using it in, i.e. dusty, sandy, hairy etc. When I opened up my 2010 iMac 27" to install a Samsung SSD, I was horrified to find both fans heavily clogged, which looked far worse on the fan hot air exit side when I removed them for cleaning - and I always thought I was in a relatively dust-free home.
Must confess I never experienced the iMac freezing, and never monitored the temps before or after cleaning, but with the clogged debris found in the fans it's amazing I never experienced what you're seeing. That could possibly explain your overheating.

I'm using it in your typical house environment in NY, not anything extreme. The rooms and the stuff in the house can get dusty but it is the average thing that every house has. We already know that the iMacs have a horrible air ventilation and they accumulate a great amount of dust. My first iMac experienced the dust spots on the screen and my current iMac had this issue but thankfully I replaced the screen under AppleCare some moths ago, so I'm sure they cleaned up everything when they took the computer apart. Sadly, I don't have AppleCare anymore and I'm not good in tinkering with the components of the machine or doing upgrades by myself.

So, I performed a clean install and restored all of the files and apps from my Time Machine backup, and will wait to see if I experience again the freezing issues, but it seems I am getting the same high temps like before. I am posting some screenshots of the temp readings and how many processes are running on the computer right now, maybe that way somebody can tell me if those high temps are normal?

 

[Azrael9]

I've tried booting my iMac 2012 (late) back. It still hangs. I've tried 'everything'. Apple diagnostic. PVRAM. Safe mode. Booting from terminal. Remote Mac OS install. All of them hang 'perma' load bar.

Yet, I can boot into PC 'safe mode' np. Normal pc mode has green and pink flecks. Screen saver says I have no open gl.

My original OS would have been Mountain Lion. I upgraded to High Sierra. My external SSD has High Sierra on it. It won't boot from that either. 'Hangs.'

I can't take it to a UK Apple store in the current crisis. It's taught me a lesson in terms of having 'back up' machines if your main rig goes down.

I did manage to get the Apple Chime back with the SMC check.

Do wonder after 7.3 years just how much dust is in there. Clogging things up? Eg. Fans etc.

There was one thing that came up that people don't mention. Do the iMacs come with a battery for the Date and Time (like the old PPC Macs did?) That stopped my 1997 rig from booting. I heard the 2011 iMacs had batteries for date and time and replacing this DID fix a booting problem.

Azrael.

 

[casperes1996]

I'm using it in your typical house environment in NY, not anything extreme. The rooms and the stuff in the house can get dusty but it is the average thing that every house has. We already know that the iMacs have a horrible air ventilation and they accumulate a great amount of dust. My first iMac experienced the dust spots on the screen and my current iMac had this issue but thankfully I replaced the screen under AppleCare some moths ago, so I'm sure they cleaned up everything when they took the computer apart. Sadly, I don't have AppleCare anymore and I'm not good in tinkering with the components of the machine or doing upgrades by myself.

So, I performed a clean install and restored all of the files and apps from my Time Machine backup, and will wait to see if I experience again the freezing issues, but it seems I am getting the same high temps like before. I am posting some screenshots of the temp readings and how many processes are running on the computer right now, maybe that way somebody can tell me if those high temps are normal?

Your temperatures are really perfectly fine. Official numbers for these sorts of things are always in Celcius, but the Intel chip is rated for up to and including 100°C, at which point it'll reduce its speed. Even without the fan being above idle, you're keeping yours below 85, far below Intel's rated limit. And that's not a hard limit at 100°, that's just a limit for normal high performance. There's headroom above that before you reach automatic shutdown.

The GPU is rated for up to 105°C before throttling, and 110°C for automatic shutdown; At least the R9 295X was.

Your temperatures really don't seem to be the issue.

 

[AlexGraphicD]

Thanks for your input and the reassurance about the temperatures, I guess I’ll wait and see if the issue comes up again and learn to be less stressed about those high temperature levels haha.

 

[AlexGraphicD]

Ugh, iMac hung up on me again... Last option I can try clean install a previous version of macOS like Mojave and see if it performs better.

 

[AlexGraphicD]

Update: I don't know what changed but the freezing stopped and the average temperature is lower from 140F to about 107F and that makes me so much happier now.