So my PS4 was getting super loud playing Bloodborne (which apparently isn't uncommon) but it was annoying. Also my console is only 2 weeks old so it wasn't dust or anything.
Yes, I know this voided the warranty.
Took it apart, it was fairly simple and the interior is a lot like the PS3's which I've replaced the TIM of too so that was handy, plus I watched a couple of teardown videos first too.
Board image for some context / visualization:
Anyway, the TIM on it was...