Abstract: A stop-leak sealant composition for an internal combustion engine cooling system, hot water heating systems and the like consisting essentially of ginger rhizome flour, ground nut shells, boric acid, with or without additives to improve performance and more particularly with a fluorescent water-soluble leak detectng additive to detect leaks that cannot be stopped by the sealant composition.

Abstract: A stop-leak composition for an internal combustion cooling system, hot water heating systems and the like consisting essentially of ginger rhizome flour, ground nut shells, boric acid, sodium lignin sulfonate and magnesium stearate.

Abstract: A method for precoating a plug adapted to close off core openings in an internal combustion engine with a plastic which forms a fluid tight seal between the peripheral surface of the plug and the core opening upon insertion of the plug therein. The plug is preferably coated with a solution of vinylidene chloride-vinyl chloride copolymer in cyclohexanone which is cured by heating for twenty minutes at 160.degree. F (71.degree. C). The thickness of the plastic coating may be doubled by heating the coated plug for ten minutes at 250.degree. F (121.degree. C).