Engine Coolant Analysis: What It Detects and Why It Matters for Backup Generators

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Why Coolant Analysis Matters for Modern Diesel Engines

The Increasing Demands on Engine Cooling Systems

Industry estimates that 50% of all premature engine failures are associated with a deficiency in the cooling system either by chemical or mechanical issue. This will cause acid formation or scale deposits resulting in damage to other components.

Today’s diesel engines produce a greater amount of power and higher operating temperatures as high as 250°F. This places a greater burden on the cooling system to absorb heat transferred from the engine, transmission and hydraulic fluids.

The result of these higher operating temperatures make careful cooling system maintenance critical to avoid engine damage from boiling, deposits, pitting or acid formation. As a result, the cooling system is becoming an even more critical component in the health and well-being of both the engine and the vehicle.

What Can Engine Coolant Analysis Detect?

Four Primary Goals of Coolant Testing

A structured engine coolant analysis program can help maintenance teams:

• Determine if a coolant is in a suitable condition for continued use
• Predict premature failure by monitoring trends and abnormal changes in the coolant
• Identify component or system failure: localized overheating and hot spots, EGR cooler failure, blown head gaskets, grounding problems, blocked coolant passages, blown head gasket, electrolysis
• Identify outdated or insufficient maintenance practices and procedures

Proper cooling system maintenance is essential to achieve the goal of optimum equipment performance and longevity. Coolant analysis is critical to maximizing both of these goals and highly recommended for today’s modern fluids that serve the system. The following cooling system guidelines are designed to help operators and fleet maintenance personnel maintain and control cooling system maintenance procedures and identify problems before engine failure occurs. If failure does occur, they can provide valuable insight as to the cause.

At increased operating temperatures, improperly maintained coolants will become acidic with time. The hotter the system, the more acidic the coolant will become. This turns the engine into a wet cell battery. The coolant becomes the electrolyte between dissimilar metals in the engine and cooling system.

Pressure raises the boiling point of the coolant about 2.7ºF (1.6ºC) per pound of pressure at sea level. Coolant boiling points drop about 3ºF (1.7ºC) per every 1000 feet above 5000 feet elevation.

About 80% of preventable engine failures caused by a cooling system problem are due to one of the following:

• Water used to mix coolant concentrate that doesn’t meet ASTM and engine manufacturer specifications for use in engine coolants
• Contaminated water used to flush a system and not completely removed
• The coolant isn’t designed for the goal intended
• Internal or external air entering the cooling system, system pressure is insufficient or dissolved gases are present from air-pitted metals or gasket failure
• Localized overheating or hot spots in the cooling system due to scale formation, EGR issues, improper pressure, maintenance errors

One-tenth of an inch of calcium silicate scale has approximately the same insulating potential as three to four inches of cast iron. The greatest amount will form at the point where the greatest heat transfer is needed. Coolant will expand to 4.7% of its total volume at 180ºF. Newer higher operating temperature engine coolants expand about 6%. Distilled water vapor is always given off through the overflow.

Common Cooling-System Problems Identified Through Coolant Testing

Today organic acid extended life and hybrid extended life coolants are more commonly used. There are many benefits to the newer formulations in terms of cooling system protection, heat transfer and cost of operation. All of these formulations require cooling system testing and analysis to assure that they are operating adequately and properly protecting the system and its components.

Organic Acid Technology Coolants

Carboxylate acid-formulated extended life coolants protect against corrosion by chemically interacting with the metal surfaces. This chemical reaction extends the life of the coolant, protects aluminum surfaces at higher temperatures and provides better heat transfer. But it doesn’t make the system any less vulnerable to the premature engine failure. Only regular coolant testing and analysis will detect a mechanical problem such as an air or combustion gas leak, electrical ground problems, localized overheating/ hot spot or operator/ maintenance error.

All of these issues can seriously degrade coolant composition and affect performance.

Hybrid Organic Acid Technology Coolants

Hybrid extended life coolants are a combination of inorganic and organic inhibitors. Unlike the organic acids which interact with the metal, inorganic inhibitors such as nitrites, nitrates, molybdenum, phosphates, borates and silicates provide corrosion protection by forming a protective layer on the various metals in the cooling system. Regular testing will detect any mechanical problems affecting cooling system operation, inhibitor depletion rates, coolant mixing is occurring causing depletion of inhibitors or when the coolant should be changed.

The most common factors that contribute to the deterioration of any type of coolant are heat transfer deficiencies, improper top-off with only water or a different coolant formulation, adding Supplemental Coolant Additives (SCAs) to an ELC and an over/ under concentration of inhibitors.

These factors can cause extensive yet preventable cooling system problems and identifiable through proper testing and analysis, which should be a consistent part of any cooling system maintenance program.

Building Coolant Analysis into a Preventive Maintenance Program

A disciplined coolant analysis program is one of the most practical ways to respond. It helps teams protect equipment, make smarter replacement decisions, and preserve reliability when supply conditions are less predictable.

Always match the coolant to OEM requirements, follow the product’s stated concentration limits, and use lab data before deciding whether to correct, replace, or continue using coolant in service.

Ready to strengthen your reliability strategy?

Bureau Veritas provides analytical fluid analysis across data center, nuclear, coal, natural gas, wind, and solar operations, helping operators protect critical cooling, lubrication, insulation, and fuel systems.

📩 ocminfo@bureauveritas.com

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