BuffaloPunch

Hello Anyone. i have a LBZ Duramax, and i have just put in a new water pump and rebuild the oil cooler and the pipe that connects them i put in after and i pitched a gasket and it eakd then i took it out again and put two non OEM gaskets on there and it seemed to stop leaking when i added coolant but when i fired it all up it pissed out again so my question.. what is the propper way to put the pipe in, i could no imagin putting it in the cooler then putting it back on the truck, do you put it on the water pump first maybe then put it in??? or can you some how use gasket maker instead??? i need help