overheating...

so i've changed my oil, put a new air filter in, and cleaned out my fuel injectors and such.... i was lookin at the coolant container on my z24 engine and noticed that one of the three tubes coming from it are disconnected from somwhere... now the one to the engine is connected and the one leading to the radiator is connected, but i dont no where the third one next to the engine tube is supposed to be connected... help please!!

Might be heater core.

not sure about the 2.4 but on the 2.2 the 3 hoses coming off that reservoir are 2 thin ones on the top and one thick one on the bottom. 1 of the thin ones taps right into the upper radiator hose, right before the coolant temp sensor, the second thin hose is attatched to the top of the radiator (i believe, this is the only hose i cant see both ends of) and the 3rd, larger hose on the bottom taps right into the lower radiator hose