That vent system is totally separate from the coolant system. The hose should be hooked to the motor to keep water, sand, dirt, etc. out of the trans.
Hose from the neck of the radiator to the bottom of the overflow, hose from the top of the overflow back up the steering stem and made to drip on the exhaust . The only way it empties is when it cools it will pull a vacuum and draw coolant back into the radiator. if the radiator was low to begin with. You're tank might just leak. It's really not needed, as long as your hose from the neck drips on exhaust you will be able to smell it if it boils over.