01 pathfinder coolant issue

[Irishpatty01]

I recently posted of my new pathfinder that i just swapped a jdm engine in. Everything seems to run accordingly, but i think i'm having a coolant flow problem. My upper radiator hose and all other metal lines and radiator are getting extremely hot but lower radiator hose isn't even warm. I tried the bleeding the air out of the system but even hot it didn't come out of the bleeder line without giving it some throttle. I'm trying to get this thing up and running asap wife's other car is failing quickly thnxs

[Irishpatty01]

Also as far as the heater core content ive ran the line from behind the engine coolant line to the lower heater core line and ran the upper to the side coolant line was this correct