Late 2009 iMac i7 2.8Ghz 8GB RAM. A couple of hours ago, I upgraded the OS from SL 10.6.8 to Mavericks 10.9.4. Immediately after the upgrade completed, the iMac was red hot. I repaired permissions and shut it down to let it cool off. I turned it back on after it cooled off and immediately repaired permissions again. Very soon, the iMac was running extremely hot again. I can feel it very hot to the touch. It's cool in the room, so that's not it (it's evening). According to iStatPro: HD: 142 F CPU: 133 F GPU Diod: 190 F GPU Heatsink: 181 F Mem Controller: 130 F Power Supply 2: 140 Fans: HD 1798 rpm CPU 2921 rpm I can hear the fans running full speed. I'm not running anything special - and remember, it was already extremely hot right after the upgrade, before I even logged in. I looked at Activity Monitor and I don't see anything special, except for a process called "mdworker" at 30% CPU... could that be responsible? Is it like spotlight or something? Should I be concerned?