All coolants come with an Active Ingredient we generically call Supplemental Coolant Additives, or SCA. The purpose of this ingredient is to make good quality water less corrosive to your cooling system. It does not make poor quality water acceptable. It also cuts down on what is known as “liner pitting” in wet linered engines.
The products have been around for many years and greatly extend engine life in terms of cooling system corrosion. But the active ingredient in these products dissipates over a period of time. When that happens, they need to be replenished in your cooling system. There are many SCA products available: Nalcool, DCA and Racor to name a few. It is important to consult your Operator’s Manual or local dealer to find out which ones are acceptable in your engine.
The way to determine the level of SCA in your cooling system is to use a test strip designed for the purpose. It will tell you the level of corrosion protection in your coolant. When low, you add the appropriate amount of SCA. This is very useful and, indeed, essential to getting the expected life from your engine.
A simpler way of doing this is to just drain and refill the coolant in your system annually. If you use a good quality coolant, the SCA is already in there. Of course, if your engine holds a great deal of coolant, it is more cost effective to replenish the SCA.
If you fail to keep the levels of SCA up, the consequences are corrosion and liner pitting. Liner pitting is the natural result of the combustion process in wet linered engines. It manifests itself as 2 vertical rows of pitting 180 degrees opposite from each other on the outside of the liner. It occurs when vapor bubbles collapse due to the expansion of the liner. SCA coats the liner and reduces or eliminates the pitting.
Is there the possibility of “too much of a good thing”? Unfortunately, yes. The SCA have to stay dissolved in the coolant and held in suspension. If you get too much in the coolant, certain parts of the mixture will “drop out”. They crystallize and float around in your cooling system. They can lodge in water pump seals, causing them to leak, among other things.