So I have a mining farm with 3 coolers and 7 graphics cards, but it still somehow overheats. After a while, it explodes. I've already lost about 3000 points because of material costs. Why is it happening? Version 09d

The miners seem to heat up a lot faster in 0.9, so you should definitely invest in more coolers before you start adding more GPUs. They also now have a limited amount of points they can hold at a time, and if that limit is reached, they will begin rapidly overheating.