Reply To: Cast Iron Furnace Pinhole Leak

I repaired my cracked cast iron radiators for a hot water heating system with epoxy putty ten years ago. They are still holding up. I would certainly give that a try if no one else comes up with a better idea. JB Weld, available in auto parts stores, is designed to be used on engine blocks which get very hot. I have heard of people successfully using it to repair cracked engine blocks.