Why is my car leaking coolant so bad?

You know we can't see it over a computer. It sounds like the hose you might be referring to goes to the reservoir. If that is not attached, coolant will run out when the engine warms up, and it will draw air back in when the engine cools down. That air can cause the thermostat to stay closed which will result in overheating and possibly expensive engine damage. This should be looked at right away. Fixing a simple leak could cost a lot less than major engine damage.