[Rafagon]

My iMac (27", Late 2009, running OS X El Capitan 10.11.2) is running hotter than usual. I launched the Activity Monitor and I noticed that UserEventAgent, launchd, and mds_stores were using a lot more CPU power than usual.

Here's the interesting part: when I eject my external hard drive, these three processes drop back to normal CPU usage and the Mac's temperature quickly drops back to normal. If I re-mount the external hard drive, the processes get busy again and the iMac's temperature begins to rise.

This just started today, and I haven't installed any new applications or done anything else that I can think of that might be causing this.

I've rebooted, but the problem persists.

Any idea what I should try next?

[Alrescha]

I had this exact problem, which seemed to start when I upgraded to 10.11.2. Whenever I see mds and friends acting up I suspect a problem with the spotlight index. I deleted mine, and that calmed down UserEventAgent. Of course all the mdworkers fired up to rebuild the index, but that looks normal in comparison.

If you want to try this, you need to use the mdutil program in Terminal, e.g:

sudo mdutil -E /Volumes/yourexternalvolumename

or to clean them all out:

sudo mdutil -E -a

The sudo command will prompt you for your password.

Best,

A.

nb: I've had the problem recur, so this isn't a simple problem of a random corruption of the Spotlight data. The good news is that toggling indexing off and back on seems to solve the problem (much quicker than rebuilding the index after an erase. I use mdutil -i off /, then mdutil -i on /.

addendum: This problem seems to appear when Time Machine runs.

addendum(2): The solution may be to exclude certain busy directories from Spotlight, such as Library/Application Support/Steam.