cooling system help please

[lumberman]

I have purchased a 1987 half tonne with a 350 in it, and cant seem to find out why i am losing so much coolant. It doesnt lose any when its not running, but when i start it up it seems to drip quickly off of the lower rad hose.I changed the lower rad hose and clamp but it still seems to be leaking out the same amount. I try to fill the system but the upper hose never seems to have any fluid in it. The truck never overheats but if i dont add fluid every couple of days, i lose heat to the cab. After taking a long drive, i get out and check that upper rad hose and its still empty and it feels like the little bit of fluid near the engine is boiling. As the engine cools down it drains the coolant from the overflow bottle. Any advise on what it could be??? As you can tell i am not a master mech and any help would be great!