Engine Water with alot of pressure

[Pingaz]

Well after a run, the pipes doesn't get rock solid, half rock solid

I don't have to much pressure in the radiator when its hot. What happens is that water gets out through the radiator cap, but its the cap itself i belive.

I had the matrix changed probably the connection wasn't pressed all the way ? But could the pressure blow out the connection ? Could it be the headgasket ? I didn't really see if the pipes are rock solid. I have to see. I have to flush the cooling system again