I poured new coolant into the radiator and after a few mins I notice coolant dripping behind the housing. I did put a new gasket and I also put some Indian head sealant to hold the gasket on the housing. The bolts are tight and I did clean the housing and base before I installed it. I don't know why it is leaking? Do I need to use regular rtv on the gasket or should I have installed the gasket dry or no gasket just rtv?