2025 International LT Coolant Capacity & Type

The 2025 International LT typically holds between 70 and 75 quarts (66.2 to 71.0 Liters) of coolant in its cooling system, depending on the specific engine configuration and options.

Quick Answer

• Total Cooling System Capacity: 70–75 quarts (66.2–71.0 Liters)
• OEM Coolant Spec: Predominantly uses a Red/Pink, Nitrited Organic Acid Technology (NOAT) ELC (Extended Life Coolant), often meeting Cummins CES 14603 or International Truck's own coolant specifications for heavy-duty applications. Always verify with your owner's manual or International documentation.
• Mix Ratio: 50/50 prediluted coolant or 50% concentrate mixed with 50% distilled water.

Capacity by Engine Option

The International LT can be equipped with various engine options, primarily from Cummins and Navistar (International). Coolant capacities may vary slightly:

Always consult your vehicle's specific owner's manual for the most accurate capacity information.

Flush Interval

Maintaining the coolant flush interval is crucial for the longevity of your 2025 International LT's cooling system.

• Normal Duty: Typically, an Extended Life Coolant (ELC) like the specified NOAT coolant can last 600,000 miles (965,000 km), 12,000 hours, or 6 years, whichever comes first. This applies to most long-haul applications under ideal conditions.
• Severe Duty: For vehicles operating under severe conditions (e.g., extreme temperatures, constant heavy loads, frequent idling, dusty environments, or vocational applications), it's advisable to inspect and potentially test the coolant more frequently and consider replacing it every 300,000 miles (482,800 km), 6,000 hours, or 3-4 years, whichever comes first. Regular testing with coolant test strips can help determine the coolant's condition and additive levels.

How to Refill & Bleed

Refilling and bleeding the cooling system on a heavy-duty truck like the International LT requires attention to detail to ensure all air is purged:

1. Safety First: Ensure the engine is cool. Wear appropriate personal protective equipment (PPE) such as gloves and eye protection.
2. Drain Old Coolant (if flushing): If performing a flush, thoroughly drain the old coolant from the radiator and engine block drain plugs.
3. Refill: Slowly add the correct type and mixture of new coolant (50/50 prediluted or 50% concentrate with distilled water) into the surge tank/radiator fill neck. Fill until the level is within the "cold fill" marks.
4. Start Engine & Circulate: Start the engine and let it run at a high idle (around 1000-1200 RPM) with the heater on full blast (to open the heater core circuit). Keep the radiator cap/surge tank cap off.
5. Burp Air: As the engine warms up, the thermostat will open, and coolant will begin to circulate. Watch for air bubbles escaping from the fill neck. Gently squeeze the upper and lower radiator hoses to help dislodge air pockets.
6. Maintain Level: Continuously monitor the coolant level in the surge tank and add more as needed to keep it between the "cold fill" and "hot fill" marks.
7. Check for Bleed Screws (if applicable): Some heavy-duty engines may have specific bleed screws at high points in the system (e.g., near the thermostat housing or on certain plumbing). Consult your service manual for their location and opening procedure. Open these sparingly to release trapped air, closing them as soon as a steady stream of coolant emerges.
8. Vacuum Fill (Recommended): For best results on modern heavy-duty trucks, consider using a vacuum-fill tool. This method evacuates all air from the system before drawing in new coolant, significantly reducing the risk of air pockets.
9. Final Check: Once the engine reaches operating temperature and no more air bubbles appear, install the surge tank cap/radiator cap. Allow the engine to cool completely, then recheck the coolant level and top off if necessary.
10. Monitor: Over the next few drive cycles, frequently check the coolant level in the surge tank and top off as needed until stable.

Common Cooling System Issues for this Generation

Owners of 2025 International LT trucks, along with similar generation heavy-duty vehicles, might encounter some common cooling system issues:

• Coolant Leaks: Due to the extensive plumbing and connections in heavy-duty truck cooling systems, leaks can occur at hose connections, O-rings, radiator tanks, water pump seals, or EGR cooler lines. Regular inspections are vital.
• EGR Cooler Issues: Exhaust Gas Recirculation (EGR) coolers are a common point of failure in modern diesel engines. Internal leaks can introduce coolant into the exhaust or combustion chambers, leading to white smoke, coolant loss, and potential engine damage. External leaks are also possible.
• Radiator Clogging/Damage: Over time, debris can accumulate in the radiator fins, reducing cooling efficiency. Internal clogging from neglected coolant changes or incompatible coolants can also occur. Road damage to the radiator or charge air cooler (CAC) is also a concern.
• Thermostat Malfunctions: A stuck-open thermostat can cause the engine to run too cool, impacting fuel efficiency and emissions. A stuck-closed thermostat can lead to rapid overheating.
• Water Pump Failure: The water pump is a critical component for coolant circulation. Bearing failure, leaks from the weep hole, or impeller issues can lead to overheating.
• Sensor Failures: Coolant temperature sensors or level sensors can fail, leading to inaccurate readings on the dashboard or triggering false warning lights.
• HVAC System Leaks/Malfunctions: Issues with the cabin heater core or associated plumbing can lead to coolant leaks inside the cab or insufficient heat.

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