Updated: Sep 27, 2019
You may think "shoot, I live in the PNW, it hardly freezes, and I park my car in the garage, I don't need to worry about changing my coolant". Today at PNW Automotive Inc we're replacing a head gasket on a 2007 Honda Odyssey, with less than 150k on the odometer. What gives? Did you know that your coolant breaks down over time? The pH or acidity level changes over time and the more acidic your coolant the more likely you are to degrade your gaskets, seals, and cooling system exposed to the substance. A pH of 7 is generally considered neutral, while a pH below 7 is considered acidic, and anything over 7 is alkaline. Water has a pH of 7.0 and full strength antifreeze has a pH of 10.5, so a 50-50 mix has a pH of 8.75, and that’s too acidic to protect the cooling system, so the pH must be modified to something around 9.5-10 to protect the dissimilar metals in the modern cooling system. As the pH drops, acidic coolant can eat away and erode gaskets, rubber, solder joints, steel, and aluminum, including head gasket material and even the material of your internal engine. The general recommended maintenance interval is to flush the coolant in your vehicle every 2 years or 30k, however, each manufacturer recommends a different interval, and even then your vehicle may need to follow a different guideline. Your best choice for prevention of a head gasket failure is to keep an eye on your temperature level. If you notice it changing at all, that's an excellent sign maintenance is needed. The second most important thing for you to do is be sure to ask for that information every time you go to the mechanic. Hopefully your mechanic offers complimentary basic inspections with every service. If they do, they should be able to find out what pH your cooling system is at. Always remember your cooling system is a closed system, it should never ever be low, or overfull. If you notice either of those situations be sure to get it checked out right away!