2020 International LT — Coolant Capacity & Type

The 2020 International LT holds between 44 and 56 quarts (41.6 to 53 liters) of coolant, heavily dependent on whether it is equipped with the Navistar A26 or the Cummins X15 engine, as well as the specific sleeper and heater core configuration. As an ASE-certified master technician, I regularly service these Class 8 workhorses, and maintaining the correct coolant level, chemistry, and schedule is critical to preventing catastrophic diesel engine failure.

Below is your comprehensive guide to the cooling system in the 2020 International LT.

Quick answer

• Total Cooling System Capacity: 44 to 56 quarts (41.6 to 53 liters / 11 to 14 gallons) depending on engine and chassis configuration.
• OEM Coolant Spec: Heavy-Duty Extended Life Coolant (HD ELC). Specifically, Nitrite-Free OAT (Organic Acid Technology) coolant, typically Red or Yellow in color. Look for Navistar CEMS B-1 Type III or Cummins CES 14603 approvals.
• Mix Ratio: 50/50 pre-mixed with deionized/distilled water (or a 50/50 concentrate mix) to ensure freeze protection down to -34°F (-37°C).

Capacity by engine option

The exact amount of coolant your LT needs varies slightly based on the block size and secondary heating systems (like a sleeper cab heater). Here are the general ranges:

Note: Always fill to the "MAX" or "COLD FULL" line on the surge tank. It is best to have extra coolant on hand due to variations in aftermarket APUs or extended sleeper heater lines.

Flush interval

Modern Heavy-Duty Extended Life Coolants (ELC) are robust, but they still degrade over time, especially under the immense thermal load of heavy hauling.

• Normal Duty / OTR Highway: Replace coolant every 600,000 miles, 12,000 engine hours, or 6 years—whichever comes first.
• Severe Duty / Vocational / High Idle: If you run heavy vocational loads or idle frequently, consider cutting this interval down to 300,000 miles or testing the coolant chemistry every 20,000 miles to ensure additive package integrity. (Note: Many modern OAT coolants do not require Supplemental Coolant Additives (SCAs), but you must test for contamination and freeze point).

How to refill & bleed

Bleeding a large heavy-duty diesel cooling system is not like bleeding a passenger car. The massive EGR coolers and dual heater cores can easily trap air pockets, which will lead to localized boiling and cracked cylinder heads.

1. Drain the System: Open the radiator petcock at the bottom of the radiator. Remove the surge tank cap to speed up the flow. If doing a complete flush, remember to drain the engine block via the block drain plugs.
2. Use a Vacuum Fill Tool (Highly Recommended): For Class 8 trucks like the International LT, utilizing a heavy-duty pneumatic vacuum coolant filler is the safest way to refill. This tool pulls the entire cooling system into a deep vacuum, ensuring that when the new coolant is introduced, it instantly fills every void in the massive EGR cooler and sleeper heater lines without trapping air.
3. Manual Fill (If vacuum fill is unavailable): Slowly pour the 50/50 ELC mix into the pressurized surge tank. Pause frequently to let air bubble out.
4. Bleed the System: Turn the cabin heater and sleeper heater on to maximum heat. Start the engine and run it at high idle (around 1,000 - 1,200 RPM).
5. Monitor and Top Off: As the thermostat opens (usually around 180°F - 190°F), the coolant level in the surge tank will drop. Top it off to the cold fill line and secure the cap. Drive the truck under load and recheck the level after the system has fully cooled down.

Common cooling system issues

For the 2020 generation of the International LT, watch out for the following cooling system weak points:

• EGR Cooler Leaks: Both the X15 and A26 can suffer from EGR cooler degradation over time. If you are losing coolant but there is no external leak, the coolant is likely being burned through the exhaust via a cracked EGR cooler. Look for white smoke or a sweet smell from the stack.
• Coolant Level Sensor Failures: The sensor inside the pressurized surge tank is prone to scaling or electrical failure, leading to false "Low Coolant" warnings and sudden engine derates.
• Water Pump Weeping: While relatively durable, the water pump seals can begin to weep prematurely if the truck is subjected to high belt tension issues or if the coolant becomes acidic due to neglect.
• Radiator Tank Seam Leaks: Due to chassis flex under heavy loads, the plastic-to-aluminum crimp seams on the radiator tanks can occasionally develop pinhole leaks.

If you are dealing with a mysterious coolant leak or need a professional flush on your International LT, don't risk your engine. Find a trusted shop on Repairius.