I have an old MBP (early 2011) that I run in clamshell mode together with a thunderbolt display. In the last few months I have noticed the fans speeding up when downloading, installing apps etc. And sometimes it just happens randomly. When checking Activity Monitor there is nothing that stands out. I have reset the SMC and installed SMC Fan Control. Nothing has helped. The temperature is around 60-70 celsius when the fans speeding up. Any ideas???