Weird behavior from 2011 iMac, is it dying?

[smurray]

I purchased a used 21.5" iMac over the summer for my wife. We were in need of a desktop, and it was really cheap on Craigslist. I've been noticing some weird behavior over the past few weeks. It started with the iMac reporting that there was no boot device randomly a couple of weeks ago. I thought maybe the HDD had died, but I was able to use recovery mode and disk utility to erase the drive and reinstall macOS. I ran a diagnostic on the drive and it reported it was fine. I wrote it off as a freak occurrence and used it as an excuse to install High Sierra cleanly. I thought everything was going smoothly, but then I noticed the wifi started randomly dropping. At one point, even though wifi was enabled, it couldn't see any available hotspots. Plugging in an ethernet cord didn't help. It didn't detect the connection. I tried resetting the PRAM last night, and the internet issues seemed to resolve itself. This morning though I noticed the internet speed slowed to a crawl on the iMac, even though it was fine on other devices on the network.

Another issue I've noticed is some strange behavior from random applications. A lot of apps seem to hang and require me to force quit and restart. I also get a lot of laggy/slow response when trying to use various apps.

I'm sorry for being a bit vague, but it's really difficult to pinpoint exactly where/what the issue is. I did run an Apple Hardware Test, and everything came out clear. Do any of these symptoms sound like something that could be because of a hardware failure? I know the system is a bit on the old side, and I honestly don't mind replacing it if needed. I don't want to write it off as a loss though unless I'm fairly confident it's a hardware issue that can't be easily fixed.

I've considered taking it into Apple, but I'm not sure what they'd be able to do. I honestly wouldn't want to invest much money into fixing it anyway.

 

[Samuelsan2001]

Sounds like a slowly dying HDD replace it with an ssd would be my advice.

 

[smurray]

That was my original thought, but the whole issue of the internet failing makes me question whether it's a larger issue. It seems like it happens most often when the connection is under heavy load. When I'm downloading a larger file I will see the speed drop slowly until it eventually hangs altogether. I use Edovia Screens to remotely connect to the system while I'm at work, and it's not connecting at all right now. I know my home internet is still working fine since I have eero and can check via their app.

 

[kschendel]

I'd see if there is anything interesting in the logs (run the Console app from the utilities folder). Problem is, there's tons of junk in there even when things are running normally. Try looking for something that specifically references hardware (disk errors, retry, reset, etc) rather than software glitches.

 

[smurray]

I'd see if there is anything interesting in the logs (run the Console app from the utilities folder). Problem is, there's tons of junk in there even when things are running normally. Try looking for something that specifically references hardware (disk errors, retry, reset, etc) rather than software glitches.

Thanks for the tip! I'll check when I get home, or if I'm ever able to connect remotely.

 

[tn-xyz]

Sounds like a slowly dying HDD replace it with an ssd would be my advice.

i agree. this is most likely an issue with the mechanical HDD.

get a random external HDD, install macOS, boot from it and test it for a while.
speed will be less than optimal, but it's a necessary step to make sure it's not the logic board having issues.

if the problems you mentioned disappear – apart from the speed – you know it's the hard drive and you can replace it with a SSD.