There are at least dozen threads on this topic. Either search or scroll half page down.  
Incredible, I took the time to ask Dell before buying if the liquid cooling will be quieter than the air cooled and IT IS NOT. I can hear it across the room on idle just word processor. A constant engine type pf noise (not fan). Liquid cooling from Dell is not the solution for quiet operation. Does somebody know if I can order a quiet fan and replace the liquid cooling system in the tower? Is it possible to take out the cooling system that came with the XPS 8950 and replace it with a quiet fan and if so which one?
XPS 8950, i7 liquid cooled, constant loud humming noise from pump