2024 International LT Coolant Capacity & Type

A 2024 International LT holds approximately 40 to 48 quarts (10 to 12 gallons, or 37.8 to 45.4 liters) of coolant, depending on the engine option and whether the truck is equipped with an auxiliary sleeper heater. As an ASE-certified master technician, I always emphasize that heavy-duty cooling systems are the lifeblood of these commercial trucks. Ensuring you have the correct coolant type, capacity, and bleeding procedure is critical to keeping your International LT on the road and out of the shop.

Quick answer

When servicing the cooling system on your 2024 International LT, keep these essential specifications in mind:

• Total Cooling System Capacity: 40 to 48 quarts (10 to 12 gallons / 37.8 to 45.4 liters) depending on engine and cab configuration.
• OEM Coolant Spec: Heavy Duty Extended Life Coolant (ELC). This is typically a Nitrite-Free Organic Acid Technology (OAT) coolant, usually Red or Yellow in color. It must meet Navistar CEMS B-1 Type III specifications (e.g., Fleetrite ELC) or Cummins CES 14603 (e.g., Fleetguard ES Compleat OAT) if equipped with the Cummins powerplant.
• Mix Ratio: 50/50 pre-mixed with deionized water, or a 50/50 mix if using concentrate. Extreme cold climates may require a 60/40 coolant-to-water ratio.

Capacity by engine option

The 2024 International LT is primarily offered with two distinct heavy-duty engine options. While the radiator size is standard for the chassis, the engine block capacities and auxiliary sleeper lines will cause the total fill volume to vary slightly.

Note: Trucks equipped with auxiliary sleeper cab heaters (APUs or bunk heaters) have longer coolant lines and will hold 1 to 2 extra quarts. Always purchase a little more than the stated capacity to account for topping off after bleeding.

Flush interval

Modern Heavy Duty ELC (Extended Life Coolant) is incredibly robust, but it still requires regular maintenance.

• Normal Duty: Flush and replace the coolant every 600,000 miles, 12,000 operating hours, or 6 years—whichever comes first.
• Severe Duty (Heavy hauling, extreme idling, harsh environments): Test coolant additive levels with test strips every 20,000 miles or routine PM service. You may need to add an ELC extender at 300,000 miles, with a full flush recommended closer to the 400,000-mile or 4-year mark.

Never mix conventional IAT (Inorganic Acid Technology) green coolant with the factory OAT ELC, as this will degrade the protective properties and reduce the lifespan of the coolant to standard intervals.

How to refill & bleed

Bleeding the air out of a Class 8 truck's cooling system is notoriously difficult due to the large volume, complex heater cores, and high-mounted EGR coolers. Air pockets can cause catastrophic EGR cooler failure or localized engine overheating.

1. Drain and Flush: Open the radiator petcock and engine block drain plugs. Flush the system with distilled water if changing coolant types or if the system is contaminated.
2. Use a Vacuum Fill Tool (Highly Recommended): For the International LT, using a pneumatic vacuum coolant filler (Airlift tool) is the industry standard. Connect the tool to the surge tank, draw the system into a deep vacuum, and let the vacuum pull the new 50/50 ELC mix into the system. This eliminates 99% of air pockets instantly.
3. Manual Fill Alternative: If a vacuum tool isn't available, fill the surge tank slowly. Locate the coolant bleed valve (usually near the EGR cooler or thermostat housing on the top of the engine) and open it until a steady stream of coolant flows out.
4. Warm Up: Start the engine and turn the cab and sleeper heaters to their maximum heat settings. Let the engine idle until it reaches operating temperature and the thermostat opens.
5. Final Top-Off: Shut the engine down, let it cool, and check the surge tank. Top off to the "COLD MAX" line.

Common cooling system issues

The 2024 International LT is a durable workhorse, but heavy-duty cooling systems face immense thermal stress. Watch out for these common issues:

• EGR Cooler Leaks: Particularly on high-mileage units, the EGR cooler can develop internal leaks. If you are slowly losing coolant but see no external puddles, or if you notice white smoke from the exhaust, have the EGR cooler pressure tested immediately.
• Coolant Expansion Tank Cracking: The pressurized surge tanks are subjected to constant vibration and heat cycles. Inspect the plastic tank for hairline cracks along the seams and check the pressure cap seal during every PM service.
• Water Pump Weeping: It is normal for heavy-duty water pumps to have a very slight weep hole discharge during initial break-in, but a steady drip indicates a failing internal seal that requires water pump replacement.
• Hose Clamp Loosening: Constant temperature fluctuations can cause cold-water leaks at the silicone hose connections. Regularly check and torque constant-tension hose clamps.

Proper cooling system maintenance is non-negotiable for commercial trucks. If you suspect a leak, need a flush, or require a pressure test to safeguard your engine, don't put it off. Find a trusted shop on Repairius.