If it is coming apart inside, the impeller could be working off the shaft. I'm not saying it is, but I've seen it a few times in the past. Dodges, Furds, Chubbies and so on. The fan pulls forward when the engine is running so if they come apart, the fan will pull forward and wipe out the radiator. I'd slip the belt off and release the tension. Then check the fan for in and out or lateral movement. It should spin smoothly with no wiggles. Is it possible something else was replaced and isn't lining up causing the belt to be off the pulley?