The diesel engine is a vital part of your heavy-duty truck. It converts fuel to mechanical energy, which powers and runs your vehicle. The process will make your engine produce heat that will raise temperatures in your truck’s interior if not cooled down properly.

The radiator fans, coolants, built-in heaters, and water will work to cool and regulate the temperatures in your engine and enable your truck to haul heavy loads over long distances.

If these cooling components are not working properly, your semi-trailer can overheat, damaging your vehicle's engine and other important parts. 

Stay with me as we examine the common causes of overheating in commercial trucks and their solutions to ensure your vehicle is in good condition and functions effectively.

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The Components of Your Heavy-Duty Truck’s Cooling System

The diesel engine’s cooling system comprises the following elements.

Water pump. The vehicle's cooling system contains a blend of water and antifreeze, essential for regulating the engine's temperature and preventing overheating. The water pump ensures that the coolant consistently circulates through the engine cylinders, cooling them down.

Fans. The fans rotate to draw in cold air, which cools the hot coolant in the radiator as it eliminates heat from the engine.

A radiator is responsible for transferring heat from the engine through the coolant and circulating the cooled coolant to regulate the temperatures in the engine cylinders. 

The thermostat. It opens and closes to allow the coolant to flow and regulate the engine's temperatures, preventing it from overheating and ensuring it works effectively.

The engine coolant. Different trucks will use various types of coolants to regulate the temperatures in their engine system. They can be a mixture of water and antifreeze properties, coolant additives, or air-based coolant.

The expansion tank. As the coolant absorbs heat, it expands and increases in volume. The expansion tank stores the extra coolant during the cooling process. 

How Your Diesel Engine’s Cooling System Works

When your semi-truck engine starts, the crankshaft rotates to run the axle fans and causes movement of the mixture of water and antifreeze to circulate through the engine jackets, warming the engine.

As the engine temperature increases, the thermostat expands and opens the top passway to allow the coolant to flow to the radiator for cooling. At this point, the bottom valves of the thermostat may not close fully.

Once the engine system temperatures increase and the coolant attains its maximum temperature, the thermostat's bottom valves close, and the passway to the radiator opens fully, allowing the coolant to move to the radiator for cooling.

The axle fans, driven by the crankshaft, keep rotating, pulling in cold air to cool the coolant in the radiator.

Inside the radiator, the coolant passes through a series of tubes surrounded by fins. The fins increase the surface areas for heat dissipation, allowing the coolant to cool down quickly and flow back to the engine cylinders, cooling them. 

The process continues to prevent the engine from overheating and corroding.

11 Causes of Overheating in Commercial Trucks

Your engine's vigorous moving parts and explosions produce a lot of heat, which the cooling system needs to dissipate to work effectively. 

Suppose one of the properties in your cooling system is not working properly, your engine will overheat causing damage to the gaskets and horse pipes and possibly even destroying the whole engine if not taken care of in time.

Overheating is one of the truck repair issues that can affect the performance of your big rig, reduce its lifespan, and even interfere with the productivity of your company. Let's look at some of the factors that contribute to overheating in heavy-duty trucks.

1. Low Levels of Coolant 

Insufficient coolant in your truck’s cooling system will cause your engine to overheat. The level of coolant available in your vehicle cannot dissipate all the heat from the engine cylinders and, thus, cannot cool them well.

Sometimes, the system malfunctions and leaks will lower the coolant level in your truck and will fail to supply the amount required to reduce the temperature in your engine system.

Over time, sediments may build up and deposit as debris inside the radiator's belts, hoses, or airflows. 

These sediment deposits will narrow the passages and reduce the coolant entering and leaving the radiator. The blockage will hinder a sufficient amount of coolant from entering the engine jackets, interfering with the cooling process and making your semi-truck overheat.

2. Broken Water Pump

The water pump stores the coolant and facilitates continuous flow to cool the engine and ensure optimal temperatures. 

Loose belt pumps, leaking seals, and worn-out impeller blades can make your water pump fail to function effectively.

Once you notice coolant stains below your truck or hear unusual noises from the pump area while your engine is running, these can be signs of a leaking water pump. Ensure you address them early to avoid further casualties.

3. Insufficient Oil Lubricants

Oil helps lubricate the moving parts of your engine, reducing friction. Insufficient engine oil will make the moving parts rub hard against each other, producing heat. The friction force will produce more heat than the coolant can handle, leading to overheating.

4. Damaged hoses and belts

Loose and leaking hose pipes and belts will tamper with the coolant, lowering its level in the water pump or even allowing air to enter the cooling system, tampering with the cooling process. This will reduce the efficiency of the coolant in dissipating the heat from the engine, making it overheat.

5. Faulty Radiator

The radiator fans run to increase the cold air inside the system, which is responsible for cooling the coolant rapidly to ensure it dissipates excess heat from the engine as required. 

A faulty radiator will hinder the fans' ability to cool the coolant, leading to increased temperature in your engine system.

The radiator cap releases extra pressure that accumulates as the coolant expands while dissipating heat from the engine. If the radiator cap is faulty and unable to release excess pressure, the whole cooling process will fail, and your engine will overheat, raising the temperatures in your semi-truck.

Another issue can be debris building up on the internal and external parts of the radiator. The debris on the outside will block the air spaces that allow air in and out, interfering with heat exchange. 

On the other hand, the build-up debris inside the radiator's passway will narrow the air passages, reducing the amount of coolant flowing into the radiator for cooling and resulting in increased temperatures in your truck. 

6. Failing Thermostat

The thermostat is a valve that connects the radiator and the engine. It has sensors that detect temperature changes and expand and contract to regulate the flow of the coolant into the radiator and enhance a seamless cooling process.

A faulty thermostat will fail to detect an increase or decrease in temperature and close the bottom valve or open the top passway to allow the coolant to flow to the radiator for cooling. This will cause your truck to overheat.

Sometimes the thermostat may remain stuck on one end due to faulty springs and fail to respond to the change in temperature in coolant, retarding the cooling process. 

Moreover, you can tell that your thermostat is defective if you notice the temperature in your truck increasing rapidly after starting it or fluctuating rapidly as your engine runs.

7. Clogged Heater Core

Your diesel engine has an inbuilt heater core that dissipates excess heat to regulate and cool engine temperatures. 

Sometimes, debris may clog the core and prevent it from losing excess heat, causing your engine to overheat and increasing the temperatures in your truck's interior.

8. Blown Gaskets

A faulty or blown gasket will leak coolant or oil. Increased leaking oil and coolant will lower their levels, causing your vehicle to overheat.

9. Damaged or Missing Fan Shrouds

An axle fan has shrouds attached around its head. These shrouds blow cold air into the radiator as the fans rotate, removing the heat in the coolant to ensure a seamless cooling process.

With a missing or damaged shroud, the fan will fail to blow enough air into the radiator, and the coolant will fail to cool and retain its heat. This will compromise the cooling process and make your engine overheat.

10. Presence of Air in the Lines

While repairing or replacing the hoses and belts, air may be trapped inside the airways. This air will reduce the efficiency of your coolant in dissipating heat and lowering the temperature in your engine, causing it to overheat.

11. Worn-Out Rod and Bearing

Friction will wear out the bearing supporting the connecting rod, causing it to misalign. The misalignment will cause the rod to spin out of place, causing friction that will increase the temperature in the engine system.

If the connecting rod spins out of place, you may notice a cranking voice while driving. This will increase the temperature and cause your truck to overheat due to friction.

How Can I Fix Overheating in my Heavy-Duty Truck?

To solve overheating in your semi-trailer, you need to understand the causes of the problem, seek help, or fix it on your own if the problem is simple. Here are some solutions to some causes of overheating in your truck.

• If the coolant and lubricating oil levels are low, add them to prevent your engine from overheating.
•  Flush the radiator, hoses, belts, and the water pump to remove the build-up debris clogging the airways and ensure the smooth flow of coolant.
• Inspect the fans to ensure all the shrouds are present and in the right shape.
• Clean the radiator to remove any external material interfering with the air movement.
• Regularly check the hoses, belts, and gaskets to identify and fix any leaks and damage.
• After replacing the hoses and belts, burp them to remove any trapped air that may interfere with the cooling process.
• You can also visit the nearby truck repair shop or contact your mobile truck mechanic to diagnose your thermostat, see if it is the culprit behind your truck’s overheating, and fix or replace it.
• Inspect your water pump for leaks and damage, and fix them early to secure your engine from overheating and ensure a smooth ride.
• In case of a spun rod, ensure you fix it early before it damages your engine.

Conclusion

Your journey will be cumbersome and risky if your commercial truck is overheating. Ensure you inspect your truck regularly to understand the state of your vehicle’s thermostat, hoses, belts, water pump, radiator, axle fans, coolant, oil, and crankshaft to identify errors and fix them to ensure they work well. Once you notice any causes of overheating, do not ignore them. Ensure you fix them early to avoid roadside breakdowns. Timely maintenance will help you curb any upcoming heating issues before they damage your vehicle's diesel engine and other essential parts, leading to costly repairs and replacement.  

Frequently Asked Questions(FAQs)

1. What are the Signs That My Diesel Engine is Overheating?

Some common signs that your diesel engine is overheating include increased temperature in your semi-truck interior, white smoke originating from the engine compartment, a strange noise from the engine, and increased temperature on the gauge reading.

2. Why is My Heavy-Duty Truck Overheating With the Right Coolant Levels?

While your truck may have enough coolant, it will overheat due to a malfunctioning thermostat and radiator, a faulty radiator cap, a spun rod, or air in the hoses and belts.

3. What Should I Do If My Diesel Engine Overheats?

Turn the heater on to help dissipate the excess heat in your engine. You can also pull over to let your truck cool down before resuming the journey. If the issue persists, ensure you contact your truck mechanic for help or visit a nearby truck shop to diagnose and fix it.

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