This is my second oil submerged HTPC. First one can be seen here http://www.techpowerup.com/gallery/2144.html
The original one has run for around three years with not one problem. The hardware was getting old and needed an upgrade so decided to build a new tank.
Same basic idea with some refinements. Submerged the pump in the oil to eliminate noise and make the entire computer one unit that can be removed from the oil by using the handles. Quick disconnects make is easy to remove the radiator. With the fans on low speed the machine is totally silent.