Question about computer hardware(problem) and gaming?

When I play League, my computer gets really loud. It starts revving up like it's about to blow. I imagine this is the heatsink fan. If I have my frame rate uncapped(when it exceeds 100) my computer is steadily loud. If I have my frame rate capped at 60, it only sometimes gets loud. Usually when there's a lot of stuff on the screen, but not always. However, scrolling my screen off the map makes my computer get quiet again.

Likewise with Rocket League, as soon as I open it, my computer gets really loud, but very steadily. It only quiets when I alt tab or close the game.

I brought it somewhere(not sure if allowed to say where) once for several problems, one of which they had to update my graphics card drivers. They ran benchmark on my computer. They said they fixed it, but only 1 of the problems was fixed(not the sound).

Could this be the heatsink? If yes, would getting an aftermarket/better heatsink keep my computer quiet? It's a pretty high quality gaming computer about a year(maybe 2 at the most?) old.

Also, if yes to the two above, when searching for a new heatsink, would any work for my computer? Or should I look for something to make sure it'll work with my pc?

Thanks.