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Maintaining HD Antifreeze/Coolants

With the invent of organic acid technology (OAT) life-of-the- engine coolants, maintenance of antifreeze/coolant can often take a backseat to other fluids. While OAT coolants have allowed for less maintenance, that doesn’t mean that one should ignore their coolant system completely. After all, 40% of engine problems originate in the cooling system! Let’s review the different types of heavy-duty antifreeze technologies and how often they should be maintained.

Light Duty Coolant + Cavitation Corrosion Protection = Heavy Duty Coolant

One of the differences between heavy duty and automotive engines is the presence of wet sleeve liners. Wet sleeve liners form the interface between the cylinders and the antifreeze/coolant in most heavy-duty engines (coolant coming into contact with the liner – hence the term “wet”).  However, these liners are prone to a certain type of corrosion called cavitation corrosion, or pitting (see figure to the right) Heavy duty engine coolants contain cavitation corrosion inhibitors to protect the wet sleeve liners from cavitation, but these cavitation corrosion inhibitors tend to deplete in use – that’s why heavy-duty coolants need to be maintained! Using automotive coolant or failing to maintain HD coolant can have catastrophic consequences for a HD engine.

Different Coolant Technologies = Different Maintenance

Your HD system will require different maintenance depending on the type of coolant technology you are using. See chart for maintenance recommendations depending on coolant technology.

ConventionalHighEvery Oil Change30,000 Miles or 500 Hours
SOATModerateEvery Oil Change50,000 miles or 1,000 Hours
NOATModerate-LowAnnual300,000 miles or 6,000 Hours
NAPS-Free OATLowAnnualCan Typically be maintained through top-off alone

How to Test

For routine field testing, tests strips (such as Fleetguard 3-Way Coolant Test Strips) can be used along with a refractometer to evaluate SCA levels, pH, and freeze point.

Water Quality in Coolants

I’m Not Paying for Water... You might be resistant to paying for water in ready-to-use antifreeze/coolant. After all, you look for the best unit price whether you are buying antifreeze or toilet paper: concentrate coolant allows for you to get more for less. However, you should know that using high-quality water in your vehicle's cooling system is essential for the coolant to be able to do its job: transfer heat and prevent corrosion. While it may be cheaper in the short term, using poor quality water can cost you time and money in the long term, as it can cause multiple issues within the system including scale buildup, inhibitor "drop-out," and corrosion.

Keep Your Vehicle Running Cool

Tap water may be perfectly fine for drinking, but not be suitable for use in a cooling system. Scale or salt buildup occurs in systems that are high in magnesium or calcium carbonates, which are common in tap water. Scale is likely to form on hot metal surfaces in the cooling system, and in areas that have slow or fast flow. When scale forms on the metal, it creates "hot spots"where the heat cannot pass through the metal as efficiently. Only 1/16th of an inch of scale can reduce the cooling system heat transfer efficiency by 40%! This can result in overheating of the engine and corrosion at the hot spots.

Prevent Clogs and Leaks

Use of hard tap water can also cause leaks. Certain kinds of scale buildup involve the reaction of a common inhibitor, phosphate, to form calcium or magnesium phosphate scale. This type of scale is attracted to seals and gaskets within the system and can cause leaks. In addition, high mineral content in water can cause inhibitor "drop-out." High mineral content can change the solubility of inhibitors in the solution and cause some of the inhibitors to come out of solution or "drop out." This can result in a white precipitate which can clog the radiator and reduce heat transfer.


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