Coolant flows straighr from rad to muffler?

Usually that indicates there is an issue with either a head gasket problem or a cracked block. In either case, it's not good and is going to be major surgery or engine replacement. From your description, there's no way of knowing how this might have come about. Whatever did cause it or how ever it occured, doesn't really matter at this point. You're going to need to get it fixed before you can do much more with the vehicle.