Within the last two weeks or so, whenever I play Borderlands 2 my liquid cooler (not sure if it is the pump or the fans) starts whining loudly after about 20 minutes. I have an i7 3770K at stock speeds (3.5 Ghz), an Antec Kuhler 920
In testing I've run AIO cooler without any thermal interface material applied to a much hotter running i7-3930K & had better results, so I really don't think it's a tim problem, but it's always worth the try. It's also slightly possible that over time the pump vibration may have loosened (very slightly) one or more of the retaining screws causing part of the cooler to pull away from the CPU which would definitely results in overheating.
Check out this video, https://www.youtube.com/watch?v=xzAmhlYXQmA
if the noise is similar to what you hear in the video, it's probably the pump going bad & time for a different cooler. If not, the fan that comes with the Kuhler 920 is one of the loudest on the market at full speed @ ~57dBa at 1 foot https://www.youtube.com/watch?v=kBImHkwCLJ8
- jump to about the 3 minute mark to hear the Kuhler 920 fan at max.
IMO, If it does turn out to be the 920, then just replace it with a Cooler Master Hyper 212 EVO which has better performance & is quieter than several of the AIO water coolers on the market & with a second 120mm fan added, handles overclocking my i7-3930k to 4.4GHz better than my old Corsair H100 did.