PS4 Pro loud fan after cleaning dust

Hello, I recently purchased a PS4 pro for $125 from a couple for overheating issues. The PS4 was fairly dirty but nothing that would raise concern. I cleaned the inside and outside and turn the power on, everything was working but when I start a videogame up the fan get about as loud as a box fan. I have read a couple of things online about it possibly being the thermal paste being an issue but I think it could be a failing hard drive. What are your thought? I am not an expert in console repair but I figured I could start with this. Thank you!