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Common Issues With Heavy-Duty Truck Cooling Systems And How To Fix Them

Maintaining your trucks, especially the cooling system, is crucial. This guide covers common issues & offers solutions for heavy-duty truck cooling systems.

Heavy-Duty Truck Cooling Systems

We don’t need to tell you how important it is to keep your trucks in good health, especially your cooling system. Like all other components in your truck, these can experience a range of issues that, if left unchecked, can lead to costly repairs and downtime. 

In this comprehensive guide, we will delve into common problems with heavy-duty truck cooling systems and provide detailed instructions on how to diagnose and fix them.


Why Overheating Occurs

Truck engines generate enormous amounts of heat during operation. Overheating can occur due to several factors:

Coolant Level: Ensure the coolant level is within the recommended range when the engine is cool. 

Thermostat Malfunction: The thermostat regulates coolant flow. A malfunctioning thermostat can get stuck, either closed or open, affecting engine temperature.

Radiator Issues: Clogs, corrosion, or damaged fins in the radiator can hinder heat dissipation.

Water Pump Problems: The water pump circulates coolant through the engine and radiator. If it fails, coolant circulation is compromised.

Consequences of Overheating

Ignoring overheating can lead to severe engine damage, including warped cylinder heads, blown head gaskets, and engine block cracks. It also reduces fuel efficiency and increases emissions. It can even cause accidents on the road

How to Fix Overheating

Check for Coolant Leaks: Look for visible coolant leaks in hoses, connections, and components. Repair or replace damaged parts.

Radiator Inspection: Clean the radiator to remove debris or clogs, ensuring efficient heat dissipation.

Radiator Cap: Ensure the radiator cap is tightly sealed and in good condition. Replace if necessary.

Coolant Flush: If the coolant appears dirty or contaminated, perform a coolant flush. Drain the old coolant, flush the system with water, and refill with the recommended coolant mixture.

Thermostat Check: Inspect the thermostat for proper operation and replace it if it's stuck, closed, or open.

Fan and Belt: Verify that the cooling fan operates correctly when the engine gets hot. Check the fan belt for proper tension and replace it if worn or damaged.

Coolant Level: Ensure the coolant level is within the recommended range when the engine is cool and top up if necessary.

Regular Maintenance: Maintain regular maintenance schedules, including coolant changes and inspections, to prevent future overheating issues.

Coolant Leaks

Why Coolant Leaks Occur

Coolant leaks can be a truck owner's nightmare. They typically occur due to:

  • Worn-Out Hoses
  • Damaged Gaskets
  • Cracked Radiators
  • Loose Connections

Identifying Coolant Leaks

To spot coolant leaks:

  • Look for visible coolant puddles under the truck
  • Check for a drop in the coolant level in the reservoir
  • Perform a coolant pressure test to pinpoint the source of the leak

How to Fix Coolant Leaks

Identify the Source: Locate the exact source of the coolant leak and replace damaged hoses, gaskets, or components.

Tighten Connections: Ensure all hose clamps, fittings, and connections are tightened securely.

Radiator Inspection: Examine the radiator for leaks or damage, and repair or replace it if necessary.

Coolant Reservoir: Inspect the coolant reservoir for cracks or leaks and replace it if needed.

Pressure Test: Use a cooling system pressure tester to identify less obvious leaks and repair or replace affected parts.

Radiator Problems

Why Radiator Problems Occur

Radiators play a vital role in cooling your truck's engine. Common radiator issues include:

Clogs: Debris or scale buildup can block airflow through the radiator fins.

Corrosion: Corrosion can weaken the radiator's structure and lead to leaks.

Damaged Fins: Bent or damaged radiator fins reduce heat exchange efficiency.

Effects of Radiator Problems

Radiator issues can result in inefficient cooling, which can lead to overheating and engine damage.

How to Fix Radiator Problems

Clogs: Carefully remove debris or scale buildup from the radiator fins using a soft brush or compressed air.

Corrosion: If corrosion is severe, replace the radiator. For mild corrosion, apply a suitable radiator sealant.

Damaged Fins: Straighten or replace bent or damaged radiator fins.

Regular Maintenance: Clean the radiator regularly to prevent clogs and corrosion.

Thermostat Malfunctions

How the Thermostat Works

The thermostat regulates coolant flow through the engine. It can malfunction in two ways:

Stuck Closed: This prevents coolant from circulating, leading to overheating.

Stuck Open: It causes the engine to run too cool, reducing fuel efficiency and increasing emissions, the latter leading to costly fines.

Fixing Thermostat Malfunctions

Stuck Closed: Replace the thermostat and ensure the replacement has the correct temperature rating.

Stuck Open: Replace the thermostat and choose one with the recommended temperature range.

Regular Checks: Inspect the thermostat during routine maintenance and replace it if necessary.

Water Pump Failures

The Importance of the Water Pump

The water pump circulates coolant through the engine and radiator. Signs of failure include:

Coolant Leaks: Check for visible coolant leaks near the pump.

Unusual Noises: Listen for grinding or whining noises.

Play or Wobbling: If there's visible play or wobbling in the water pump pulley, it may be failing.

How to Fix Water Pump Failures

Replacement: If the water pump is damaged or leaking, replace it with a new one.

Bearing Noise: If there's a bearing noise, replace the water pump bearing.

Regular Maintenance: Include a water pump inspection in your maintenance schedule.

Fan Belt Issues

The Role of the Fan Belt

The fan belt drives the cooling fan, aiding heat dissipation. Common fan belt issues include:

Wear: Over time, fan belts wear out and can slip, reducing fan efficiency.

Tension Loss: Improper tension can lead to slippage.

Misalignment: Misalignment can cause the belt to wear unevenly.

Fixing Fan Belt Issues

Tension Adjustment: Adjust the fan belt tension to the manufacturer's specifications and replace it if worn or damaged.

Alignment Check: Ensure the fan belt aligns properly with the pulleys.

Regular Inspection: Periodically check the condition and tension of the fan belt.

Coolant Contamination

How Coolant Contamination Occurs

Coolant contamination happens when foreign substances, like oil, grease, or rust, mix with the coolant. This can lead to:

Clogged Radiators: Contaminants can clog the radiator, reducing heat exchange efficiency.

Reduced Heat-Carrying Capacity: Contaminants can affect the coolant's ability to carry away heat.

Corrosion: Contaminants can lead to corrosion within the system.

Preventing Coolant Contamination

Use High-Quality Coolant: To prevent contamination, use high-quality, compatible coolant.

Regular Coolant Flush: Regularly flush and replace the coolant.

Address Leaks Promptly: Fix any leaks promptly to prevent contaminants from entering the system.


By understanding and addressing common cooling system issues, you can ensure your truck runs efficiently, preventing costly repairs and downtime. Regular maintenance and prompt action when issues arise are key to keeping your heavy-duty diesel trucks cool and your business thriving. 

If you ever find yourself in need of professional assistance with your cooling system or any other heavy-duty truck repair, don't hesitate to reach out to us. Our team of cooling system experts is here to keep your trucks running smoothly, ensuring a safer and more efficient journey on the road.

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