I was hoping a layout like this was going to be an isolated incident but unfortunately a design and implementation of the below diagram has come up twice this week... this design has a few issues but I'll deal with the radiators and fans today...

The users have their fans blowing fresh air into the case, through a radiator then across the motherboard. The air is then sucked though the radiator at the back of the PC. Obviously the air exiting the first radiator is heated up. This same air is then heated again as it passes other components in the case like HDDs, RAM, VRM... Finally the air is sucked thought the radiator at the back of the case. This is obviously madness - the first radiator is removing the heat from the water loop, However the second radiator is putting this heat back into the loop.

How bad is a system like this? Well the user confessed that his load temps were above 80c

The solution to the problem is to have both radiators ether blowing into or out of the case. Both have drawbacks but the temps wont be anywhere near as bad as above setup.