The cleaning compound covered by this specification is intended for cleaning water cooling systems of engines on motor vehicles. It is a two step type cleaner, consisting of an oxalic acid type cleaner to assist in dissolving and removing accumulated rust and dirt. The engine must then be flushed with a neutralizer compound. Normal maintenance procedure after the cleaning operation would be to refill the cooling system with an antifreeze containing a corrosion inhibitor or with water to which has been added a corrosion inhibitor conforming to O-I-490 (6840-584-2707).