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  • Writer's picturejianmei huang

Have a lot of questions about heavy-duty truck coolant? All in this guide

Heavy-duty trucks are the backbone of the transportation industry, and their performance is crucial. A key component ensuring their efficient operation is the coolant system. This system, responsible for maintaining engine temperature, faces unique challenges in heavy trucks due to their size and workload.

The coolant system in heavy-duty trucks plays a pivotal role in engine health. These systems, designed to regulate engine temperature, must endure the rigors of long-haul routes and heavy loads. The coolant circulates through the engine, absorbing heat and preventing overheating. This process is vital for maintaining optimal engine performance and fuel efficiency.

Preventative Maintenance

Proactive maintenance is key to avoiding coolant problems. This includes regular checks of the coolant level and the condition of the hoses and the radiator cap. A visual inspection for leaks or damage to the radiator and water pump should be part of routine maintenance. System flushes and replacing the coolant at manufacturer-recommended intervals are also crucial for maintaining system health.

The Impact of Coolant Issues on Truck Performance 

Neglecting coolant maintenance can lead to significant problems. Reduced coolant levels can cause the engine to run hotter, reducing its efficiency and potentially causing serious damage. Contaminated coolant can lead to clogging and corrosion, affecting the engine's longevity. Regular monitoring and maintenance of the coolant system are essential for preserving the truck's performance and avoiding expensive repairs.

Choosing the Right Coolant

Selecting the appropriate coolant is crucial. Factors to consider include the specific engine type of the truck, the environmental conditions it will be operating in, and the manufacturer’s recommendations. Different coolants offer varying levels of freeze protection, corrosion resistance, and heat tolerance, making the right choice essential for optimal engine performance.

Here are the main types of coolants commonly used:

Inorganic Acid Technology (IAT): This is the traditional green-colored coolant, often found in older truck models. IAT coolants use inorganic acids as corrosion inhibitors. They typically have a service life of around 2 years or 30,000 miles before they need to be replaced.

Organic Acid Technology (OAT): OAT coolants, which are often orange, red, or dark green, use organic acids to prevent corrosion. They have a longer life than IAT coolants, typically lasting 5 years or 150,000 miles. OAT coolants are particularly good at preventing the buildup of deposits in the cooling system.

Hybrid Organic Acid Technology (HOAT): HOAT coolants, which may be yellow, turquoise, pink, blue, or purple, combine the best features of both IAT and OAT coolants. They use both inorganic and organic acids for corrosion protection. HOAT coolants generally have a service life similar to OAT coolants but provide better protection for some metals.

Nitrited Organic Acid Technology (NOAT): Specifically formulated for heavy-duty diesel engines, NOAT coolants are enhanced with nitrites and other additives to provide superior protection against cylinder liner cavitation and corrosion. They are typically red or pink and offer extended life service intervals.

Nitrite-Free Organic Acid Technology (NMOAT): Similar to NOAT but without nitrites, these coolants are often used where nitrites are not recommended or are prohibited due to environmental regulations. They offer similar benefits to NOAT coolants but with an environmentally friendlier formulation.

Silicated HOAT: This type combines HOAT with silicate additives, providing extra protection for aluminum components. It's often used in European heavy-duty truck models.

DIY Tips for Managing Coolant Issues 

Drivers can take several steps to manage coolant issues. Regularly checking the coolant level and topping it up when necessary is straightforward but essential. Inspecting the system for signs of leaks, such as puddles under the truck or a drop in coolant levels, is also crucial. Keeping an eye on the engine temperature gauge can provide early warning signs of overheating.

Professional Assistance

Complex coolant system problems require professional intervention. Mechanics can provide comprehensive diagnostics to identify the root cause of issues, ensuring that repairs are thorough and effective. They have the tools and expertise to handle more intricate problems, such as internal leaks or system blockages, that are beyond the scope of DIY maintenance.

Problems That Can Occur With Heavy-duty Truck Coolant

In heavy-duty trucks, maintaining the coolant system is crucial for optimal performance and longevity of the vehicle.

Coolant Leaks: One of the most frequent issues is the leakage of coolant. These leaks can occur in various parts of the cooling system, such as hoses, the radiator, or the water pump. Leaks can lead to a drop in coolant levels, causing the engine to overheat and potentially leading to significant engine damage.

Contamination: Coolant can become contaminated with oil, fuel, or other substances. This contamination can lead to a reduction in the effectiveness of the coolant, causing overheating and potential damage to the engine. Contaminated coolant can also cause corrosion and buildup in the cooling system, leading to blockages and reduced flow.

Overheating: Overheating is a serious concern in heavy-duty trucks and can be caused by various factors, including low coolant levels, a failing thermostat, a blocked radiator, or issues with the water pump. Overheating can cause severe engine damage and reduce the truck's overall performance and efficiency.

Corrosion and Scale Buildup: Over time, the coolant can become acidic, leading to corrosion within the cooling system. Scale and rust can also build up, particularly if the coolant isn't changed at recommended intervals. This buildup can clog the cooling system and reduce its efficiency.

Air in the Cooling System: Air pockets in the cooling system can significantly reduce its efficiency. These air pockets can prevent coolant from flowing properly, leading to hot spots in the engine and potential overheating.

Inadequate Coolant Mix: Using the wrong type of coolant or an incorrect mix of coolant and water can lead to issues. Different engines require specific types of coolant, and the wrong mix can lead to reduced freezing and overheating protection, as well as increased corrosion.

Failing Radiator Cap: A malfunctioning radiator cap can lead to a loss of coolant pressure, which can subsequently cause the coolant to boil and the engine to overheat.

Thermostat Failure: The thermostat regulates the flow of coolant to the engine. A failing thermostat can stay closed, blocking the flow of coolant, and leading to overheating.

Water Pump Issues: The water pump is responsible for circulating coolant throughout the engine. A failing water pump can lead to inadequate coolant circulation, resulting in engine overheating.



Maintaining the coolant system in heavy-duty trucks is essential for reliable and efficient operation. Regular maintenance, the right coolant choice, and professional support when needed can prevent costly breakdowns and extend the life of the truck. Understanding and addressing these issues is key to ensuring that heavy-duty trucks remain a dependable part of the transportation industry.


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