Nissan Technical Advisor 1/12/2011You might be referring to a steel seal head gasket sealer? Steel Seal Head Gasket sealer. An ingenious product that claims to be able to seal blown head gaskets and even small cracks in your cylinder head. How does Steel Seal work? Steel Seal is added to an antifreeze/water mixture and poured into the radiator of a cold engine. Once the engine is started and reaches operating temperature, SteelSeal is distributed through the engine. The product is drawn into the damaged area and seals the crack with a thermo-chemical bonding action process. This is similar to that of an epoxy resin just in liquid form. I have not tried this product yet.