The other night one of my cast iron radiators cracked not on a seam but split on one of the “fins” is what I call them. It is a hairline crack. The radiators are about 85 years old, the water that drained out of the system was very clear not at all rusty. What could have caused this and can it be repaired? If so where can it be reapaired. I live in Fowlerville Michigan. The radiator is 5 ft long 18″ high 12″deep and it is not fancy the fins are kinda oval shaped and smooth with a kinda pinched ridge along the most outer edge of the fins. HELP!!!!!!! and thanks