Cooling system sealing additive. It stops leakages immediately and prevents new leakages in the cooling and heating systems of cars. It protects the combustion chamber from possible intrusion of the cooling fluid. It drains together with the coolant through the hole and polymerizes, forming a strong sealing plug. It is neutral to parts made of rubber, plastic and non-ferrous metals. It is fully compatible with antifreezes and cooling fluids.