man we have some water cooling noobs in here
for starters the water cooling should not leak because it is sealed as was stated, as for the hot water running over a cpu...what are you getting at and where did u pull that from?? did u seriously think that the water that ran over the cpu in a normal setup was hot???
also the ambient temp has nothing to do with the water cooling it can go below ambient as long as u have the right water cooling stuff(i.e peilter and good rads)
also u don't put anything else into a water cooling setuip but water and some thermal stuff to help it conduct more heat from cpu. if u put anything else in it would not work apart from the specaliesed systems that use liquid nitrogen and **** like that but that is just extreme