If it came with a fan, than it is safe to assume it needs a fan to run properly. It is quite common to have these cheap little fans die; all of mine have over the years. I keep a box of assorted replacement fans in the closet.
Some vid cards don't have a fan, but they have been tested my the manufacturer to operate stable under those conditions. Your welcome to try it, but don't be surpised when Unreal locks up.