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Do you have the broken piece, is it in one chunk or did it crumble apart? The only way I'd use liquid steel is if I had the broken part to use, but if it's lost, then I'd remove the case half and either weld it and re thread the hole mor replace as BIG DAN stated. If you do re use old broken part, make sure you file sealing surface of case flat so drain plug will seal properly. Good luck.