there's not much you can do. It's either go to a repair shop..or a friend that is knowledgeable about computer. Since you got the case open already, check the pump. Is it running, is the water being circulating. If that's working, then you check the condition of the thermal grease. Check ALL fans, make sure they are working.
Last night I left my PC on while I slept and left it on all day till about 5:00, I had never done this before. I started playing games and experienced a big fps drop and stuttering games. And then it turned off by itself, it's kept doing this for awhile. Sometimes it said "Cpu over temperature of something like that. I have the saber tooth x58 motherboard and the Intel 950. I opened my computer and saw a bubble in one of the water cooling tubes. It felt a little hot by the copy and I don't know what to do.