Chosen Solution

I cleaned out my PS4 as it had been overheating pretty often, so I went alongside a YouTube tutorial, and other written tutorials as well. I took it down to the heat sync and put it back together. I came inside set it up, and turned it on. It started with the fans on maybe medium, then they instantly went full boar while the PS4 turned off. Exactly like an overheat, any ideas on what could’ve happened?

did you apply new thermal paste? That sounds like there is not enough on there.