Greetings!

I built my Pc about 3 years ago. And it ran like a dream then. It was also quiet with the stock CPU cooler. Then obviously the thermal paste needed replacing so while i was at it i replaced the heat sink with a Dark Night cooler. That made things silent for the CPU. But now ill be playing GTA V and the fans on the GPU (im assuming GPu from watching the spike in heat according to speed fan from 50 to 71 degrees celcius ) GO nuts to a point its like a jet in here. The game continues to run just fine and everything's stable but is this normal? And is there anything i can do? ive cleaned the dust out of the PC recently too.

AMD Fx 8120 3.1GHZ
aftermarket Dark Night cooler
8GB DDR3 Ram
2x 1TB hard drives ( 1 boot OS and other personal files games ETC)
MSI hawk r6870 Twin Frozer III (i think 3)
CM STORM enforcer case
Confirm the noise is from which  fan.
Replace that fan. Or try and lubricate the fan, if you can.
http://www.techrepublic.com/article/quiet-noisy-computer-fans-with-a-drop-of-oil/
Quote

I prefer to use sewing machine oil, because, in addition to being a lightweight oil, it has excellent viscosity, holds up well at high temperatures, and is specifically designed to lubricate moving parts that operate at high speeds.