How to fix an Xbox One (1st gen) Overheating problem?

I just got a for-repair Xbox One today (first gen) very cheap off FB Marketplace. It powers up and plays the games however the Xbox case seems to get extremely hot (infrared thermometer shows 134F and rising before I shut it down). The large fan does seem to spin but it never shifts into a higher speed as it gets hotter.

When I pulled this unit apart it seems like there was some liquid spill over the fan as there was some sticky residue on the heat sink below it. I am not sure if the fan is semi-bad (so I need to replace it), or some liquid got on the CPU/GPU so I need to reapply thermal paste.

Again, even with a seemingly bad spill on the CPU//GPU area over the fan, it seems to function as it should minus the overheating problem.

I was wondering how I can fix this up?

Just like any other computer - if the fan is questionable, replace it. Once you get the replacement fan, then look into the idea of replacing the TIM for the CPU. This way you only need to take the system apart once.

https://support.xbox.com/help/hardware-network/warranty-service/getting-your-product-serviced

i hope this helps.

Just replace the fan and thermal paste.