Join Date: Apr 2010
Location: Florida / Pennsylvania
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Another Note on Coolant....
The 50/50 coolant/water mix is not just for freeze protection, but also to prevent coolant breakdown, provide efficient heat transfer, and provide adequate corrosion protection. The breakdown of glycol (the active freeze protection component in coolant) into its acidic forms only typically occurs at lower glycol percentages (10-30%). This is why maintaining 50/50 coolant/water is important. While glycol's only purpose in the cooling system is to prevent freezing, 50% water still allows for decent heat removal, and the amount of glycol (30-50%) helps prevent chemical breakdown/degradation.
Straight tap water is corrosive and distilled water is even more corrosive. Aluminum is relatively corrosion resistant within the pH range of 7.5-8.5. It does, however, corrode at both ends of the pH spectrum (<7.5, >8.5) Therefore, it is critical to maintain a pH of 7.5-8.5. The typical "green" coolant does this and is not just glycol and water. It also contains silicates, phosphates, etc. High levels of phosphate aid in stabilizing the glycol and prevent it from breaking down. The silicates provide direct corrosion protection via a filming mechanism. As the cooling system runs, the silicates create a molecular barrier (film on a molecular level that you will never see) over the metal parts, aiding in preventing the corrosion reaction. The chemical reactions involved in Silicate chemistry are complex and not completely understood, but we know that in closed loops, like an engine system, it works well.
In short, it is important to use the correct coolant/water mix in order to protect the engine. Straight water offers better cooling and heat removal, but coolant is necessary to protect the engine. Too much water or coolant could throw off the pH, corrosion protection, cooling capability or freeze protection. Its not a good idea to use 100% water, or 100% glycol, unless the system is specifically designed for it.