Computer randomly freezes

[Shvada]

When I turn my computer on, it will freeze. Sometimes after 10 minutes, sometimes after an hour. Rearly after 2 hours, but it will freeze eventually. The only way I can get it unfreezed is by restarting the computer. The computer is pretty new, I have it just over half a year. Something I thing worth mentioning is that my water cooling system broke, and before the that the computer ran smoothly no problem at all. My water cooling system broke when my computer was unplugget from power because I wanted to improve the airflow in my computer by changing the fan position.

Back to my freezing problem..
I tried to check what's the problem by opening the computer and see what the motherboard's LEDs (Q-Code LEDs) were saying when it freezes. The LEDs were saying BF, which for my understanding saying "Reserved for future AMI codes".

 

My computer specs:

 Intel core i7 5820k 3.3GHz

Asus x99-a motherboard

NVIDIA GeForce GTX 970 G1 gaming

The water cooling system:

Crosair H75

16 RAM

Windows 7 64 bit