Originally Posted by gvelarde
Thanks for your answer RON1004, I'm not an expert in cars, but searching on the internet i found that in some makes / years/ models (not necessarily the kia sedona) the water pump starts as soon you start the car and generate this compression automatically... I guess for your answer that this is not the case for the Kia Sedona right? Fixing the gasket is too expensive???
Almost all cars I know the water pump is driven off the v-belt or timing belt and run when the engine runs, but the water pumps do not generate any pressure in the cooling system - the pump of course does had a discharge pressure but that does not pressurise the coolant system.
What I understand from your description is that you have pressurised gas coming out the cooling system long before the engine has warmed up, and in that case it points towards a blown head gasket - if you had access to the car long enough before purchasing it, you'd notice that it's losing coolant.
Fixing the gasket is quite expensive and it would be prudent to get the cylinder head overhauled at the same time, or at least skimmed.