radiator coolant

The 50-50 antifreeze rule

The 50-50 rule is the rule of radiator coolant: you should have a 50% mixture of antifreeze to distilled water in your radiator’s coolant tank.  Bet you’ve wondered how essential this is though.  What is the huge deal if you have pure water in your radiator and it’s summer?  The answer is that a nasty thing called electrolysis corrosion, a

chemical reaction that occurs between a car’s coolant and the metal surfaces within your car’s cooling system, will happen. 


For example, a typical cooling system will have aluminum heads, an iron engine block, an aluminum radiator and maybe a brass heater core.  Because of those different metals being immersed in the same water path, electrophysical chemistry occurs, which means that is small electric currents will flow between the various metal surfaces.  The result of this current flow, over time, is a corrosion that will eat away at the metals. This will eventually cause small holes and leaks. 


But there’s more. Rubber hoses may also fail because of electrolysis corrosion. Rubber is usually non-conductive so you wouldn’t suspect this would be possible but the coolant can react electrochemically with synthetic rubber.  If you cut open an old radiator hose, the inside will have creases and cracks because of the electrochemical process. 


Here’s how to tell that electrolysis corrosion has occured: 


Intake manifold gasket leakage – A coolant will seep into your engine oil because of a gradual softening of the seals on certain intake manifold gaskets that has taken place over time. It might also occur due to corrosion eating away at the edges of coolant ports in the intake manifold and cylinder heads. A leaking headgasket is the unfortunate result!


Radiator leakage  There may be coolant leaking from the radiator and small, wet pinholes in the radiator’s metal components. You might possibly see coolant dripping underneath the car in tiny puddles. This is what the Service manager at Patrick Volvo, a full-service car dealer in Schaumburg, IL, told us. 


Heater core leakage  Coolant leaking from the heater’s core will typically leave wet spots or drips on the front carpet under the car’s dash.  You may also see a greasy vapor or steam condensing on your windshield when you put the heater or defroster on.  


Do you want to avoid all this stuff?  Make sure that good antifreeze with “corrosion inhibitors” is mixed in the radiator fluid. And, if it’s been more than five years since you’ve changed the coolant, drain and flush the cooling system, then refill it with a 50/50 mixture of distilled water and fresh coolant. (Do NOT use tap water because tap water can contain dissolved minerals that are corrosive and will cut short the life of the corrosion inhibitors in the coolant.)  


Face it, having a fresh anti-freeze in your car is cheap protection against the expensive repairs that can happen when electrolysis corrosion begins eating at your engine and other parts. We hope that you have enjoyed this very informative article!