i just switch the dates around so it will never get around to actually updating...
That sounds very futile. MS will ping any time server and know it has an incorrect date anyway. Just put the setting on "never" so you'll know the high-speed fan is not the cause of automatic WU checking.
...I know it had something to do with the windows update.
Yep, checking for updates is now cpu-intensive. Probably done intentionally. Actually it's probably not even checking for updates...instead it's probably solving an increasingly-harder math problem every month so that would explain the increasing amount of time needed for "checking updates" and hence the win10 conspiracy.