Hello,
The line is spliced between the water pump and the aux water pump. However, I solved the problem by driving on the highway for a bit per the directions. I guess that it just needed more pressure and heat to get the air out of the system. I think that the 3/8 line will actually work out ok now because I am getting great heat to the tank and to the heated filter. Thanks for the help!
Cheers!
Lukas