Cooling System 43 Additives Additives are part of most antifreeze and should be tested for and added to all coolant mixtures using normal antifreeze. If extended life coolant is used, the additives are in the product when mixed. Both types need to have additives added to after a time. Additives help prevent rust, scale and mineral deposits from forming. Additives also protect metals from corrosion, prevent water pump and cylinder liner cavitation and contain anti-foaming agents. Additives are depleted during normal engine operation and need to be replaced.
For normal coolant mixture, this means the addition of Supplemental Coolant Additives (SCA) at any time the additive goes below the recommended level. For extended life coolant mixture, this means an extender package added halfway through the coolant lifetime. Nitrites or nitrite and molybdate additives protect the cylinder liner from cavitation erosion. Nitrites deplete over time, creating the need for SCAs or extender. Other coolant additives also deplete and need replacement. A too low concentration of additives in the coolant will not provide the protection required by the cooling system.
A too high concentration of additives in the coolant can cause additives to solidify and drop out of the solution, depositing inside the cooling system or form a gel in the radiator. Deposits can be in the form of sludge and scale. Deposits accumulate on hot engine surfaces, reducing the effectiveness of the cooling system or causing water pump leaks.