I think you mean that the cooling jacket provided to cool the IC engine..
Actually there are Boiling and evaporation.. And the main difference in these two are.. in evaporation bubbles start forming from the hot surface.. but unlike in boiling the bubbles starts forming from the surface of the liquid which is being heated.. So in the water jackets provided for cooling of IC engines.. the cooling happens due to evaporation cooling...
@Nizar Ahammed. What you mentioned is the convective heat transfer process happening in all liquid cooling systems as the coolant temperature approaches saturation condition. But what I asked is about a cooling system which completely works based on the evaporative cooling process