Originally posted by DJIMPREZA
from the pump it goes a hose barb, then to a black tube, it will go to heater, during its travels across the engines block, this black tube has an extra hose barb, wich goes to TB, once the heater has been filled with water from pump, it will return to the cast aluminum piece wich distributes the water from both open decks galleries in the block, the same happends with the tb return line, it line up with the cast piece.
DJIMPREZA, I went to have a look at the black tube you were talking about, I think that's the return from the heater core and the cast aluminum piece on top of the block supplies coolant to the heater core.
The hose barb coming out of the pump is (I think) on the suction side and also on the engine side of the thermostate. This just means that when the engine is warming up, the coolant circuit includes the heater core and only bypasses the radiator.