> Wobbly internal hard drive
I boot my iMac 27–inch Late 2013 from an external SSD, and now its internal hard drive has become wobbly, sometimes not appearing in the Finder when it starts up. Disk Utility says it can’t be unmounted, so it can’t check it. What should I do?
You should still be able to check your Mac’s internal hard drive by restarting it in Recovery mode, opening Disk Utility there, and running First Aid. However, while that should give you a little time to ensure that it’s backed up, when a hard drive is over eight years old and starts to become unreliable you should be prepared for it to suddenly fail.
On this particular iMac, replacing the internal drive isn’t particularly difficult, but does involve separating its display and removing the left speaker. While there are instructions online, you’ll almost certainly want to get this done by an experienced service engineer.
There is another danger to consider, particularly if you replace the old hard drive with an SSD. It’s common after this procedure for the firmware to become impossible to update, and that in turn can prevent macOS from being upgraded at all.
If your iMac isn’t yet running Catalina, this might be a good time to upgrade, or the alternative is to look at replacing it with a new Mac.