Are you talking about the coolant overflow hose? It should be right under the rad cap. When you heat water it expands. The overflow system is a plastic tank that catches the expanding fluid and keeps it until the engine cools back down and draws it in.

 

well I wonder what that's for. might be a part of the mold for that part that works on another model or make and its used for this one.

 

It may be as simple as who ever made the mold for the tank made it so it could be Auto or manual. This would save in tooling cost and setups for running the parts.