Monitor engine cooling systems and coolant concentrations to achieve optimal operation during the summer months

With the primary goal of delivering a contracted load from Point A to Point B, construction fleet managers know they cannot control the weather in any region or on any route. The best they can do is prepare their vehicles to withstand whatever the road throws at them.

Extreme heat puts extreme stress on a heavy-duty truck and its engine. The primary source of protection from heat is an engine’s antifreeze/coolant (AF/C). Fleet managers understand that effective engine cooling system maintenance is their frontline defense against summer’s relentless heat, and it requires a proactive approach to testing and maintenance.

By increasing the percentage of antifreeze concentrate during winter, heat exchange properties of the AF/C are compromised and can lead to engine component troubles in the summer. A disproportionate ratio of AF/C to water in the mix can mean the heat exchange between the AF/C the engine cooling system will not be efficient, putting additional stress on the cooling system components that could lead to premature failure. This can also lead to additional stress on the other functional fluids under the hood, including engine oil, transmission fluid and power steering fluids.

In some cases, inhibitors can precipitate out and expose metal components of the engine to premature wear and potential failure. The modern heavy-duty engine is equipped with a myriad of lightweight metal components such as heat exchangers, water pumps and EGR coolers, which are all impacted by higher operating temperatures.

Given these potential problems, OEM recommendations should always be consulted. A general recommendation of a 50/50 ratio will provide the system a boiling point up to 265° F. Above a 5,000-foot elevation, AF/C should be maintained at a 55-60 percent concentrate-to-water mixture to reduce the chance of the mixture boiling over.

To optimize the performance of the specially-blended inhibitors in an AF/C, it must be accurately diluted with good, quality water. Beware, though, water quality can vary depending on the source and timing throughout the year. In some locations, it can be extremely difficult to find a water source that would meet the TMC and other industry recommendations.

Measuring and maintaining the concentrate/water ratios within an engine cooling system can help ensure optimum engine operational efficiency. Ratios can be measured a number of ways, such as with a hand-held refractometer, a hydrometer or test strips. The challenge for a fleet manager is that these measurements only ascertain whether boil point and freeze point protection are correct; it does not indicate the level of inhibitor protection.

Test strips are designed to test AF/C inhibitor levels in a vehicle’s cooling system. Qualified independent testing laboratories are another option to determine the exact condition of an AF/C sample. The primary focus when checking the engine AF/C quality in a heavy-duty diesel engine is to guarantee the concentrate and water ratios are correct and will provide boilover protection.

Having the ability to proactively test an engine cooling system is imperative to making the right decisions for maintaining the correct levels of AF/C concentrations. By providing an easy way to test an engine cooling system, essential preventative maintenance can be convenient and highly accurate.


Today’s testing kits and tools can tell you the condition of the fluid and identify component wear and contamination in engines so that you can:

• Safely extend drain intervals and equipment life
• Maximize asset reliability
• Minimize downtime (catch minor problems before they become major failures)

The heat of spring and summer will create harsh conditions and challenges to fleets across the United States. Regularly scheduled maintenance throughout the lifetime of a heavy-duty vehicle can keep it running for a very long time. Planned maintenance is the key to optimal engine cooling system operation, and fleet owners must monitor their AF/C to ensure the concentrate remains at a safe ratio and the inhibitor levels are in the appropriate range.

For more information, check out the Critical Warm Weather Coolant white paper.