I just got a 1998 Chevy 3500 6.5l, it has no heat and the antifreeze keeps going down and there isn't any in the oil. Any suggestions to what is wrong?

 

By "no heat", do you mean no heat ever? If so, have you checked to make sure the heater hoses are attached correctly, and someone didn't bypass the heater core because it has a leak?

How fast does it go down? A slow leak that leaks only under pressure can be very difficult to find without a cooling system pressure tester.

 

I don't notice it going down until it drops to the bottom of the tank. It also smells like antifreeze in front/under the hood when it's warm. I'm going to get a pressure tester.