Hi The lower hose is basically there to drain excess fluid if you overfill during maintenance. When the radiator warms up there is expansion, the radiator cap is designed to take a certain psi then it allows release of fluid to the reservoir, when it cools the fluid is siphoned back to the radiator and keeps the system in status quo. The dangling hose in there just to discharge excess fluid that will not fit in tank. Usually in cool condition the tank remains half full but if you over fill the tank during a maintenance operation the fluid volume will become too great and be discharged onto the ground through that hose. On my kubotas (3750, 5660, b7800 and rtv 900) I make sure that hose is not discharging on the tractor frame and causing corrosion, but be careful on any discharge if you have 2 legged and 4 legged animals because the antifreeze has a sweet taste and can be poisonous.