PC restarts when gaming.

[green_salad]

Hello to the community , I have had many issues with my pc in the past but I was always able to find fixes online especially on this exact forum but this time its different so I decided to make my own thread.
I have this issue with my pc for like 1,5 year now. My pc was restarting when hardcore gaming ( some games run without restart ) I had weird noises coming out of my PSU and I was thinking that that was the one causing the issue, had no money then so I just let it be like that while I was only surfing the web etc.4 months ago I changed my PSU , the issue was fixed for a little while but soon it began restarting again.
Things I tried :
-As I mentioned above changed PSU
-Formated my computer
-Reinstalled-changed drivers
-Run memtest86 for 6 hrs no issues
-Temps were always the same in the past when I had no issues with restart ( while heavy gaming cpu around 75-80 C gpu 65-75C )
-Changed HDD's
-Checked for viruses-malware etc
-Tried many fixes online about the issue like changing power managment options

Specs:
Win 10 Pro 64bit
8GB RAM 1333hz
Intel Core i5 2400k 3.1-3.3GHZ
GTX 660 OC 3GB
MotherBoard is P67A-D3-B3
PSU 850W

 

[Rhoghar]

Do you also lose signal before your PC restarts? I had the same problem and it turned out that the GPU was faulty.

 

[green_salad]

Do you also lose signal before your PC restarts? I had the same problem and it turned out that the GPU was faulty.

No game is running normally and I just restarts the same way it would If I restarted it myself with the buttom.

 

[Rhoghar]

Make sure your GPU is in a PCIE x16 slot. Have you tried benchmarking it, see if there's any issues?

 

[green_salad]

Make sure your GPU is in a PCIE x16 slot. Have you tried benchmarking it, see if there's any issues?

I havent changed the slot its the same from the day I bought it back at 2011 , yeah I run Heaven benchmark at max settings ( distortion and aa max ) for like 30 mins with no restart.