2022 Kenworth T680 Coolant Capacity & Type Guide

The 2022 Kenworth T680 holds approximately 48 to 64 quarts (45 to 60 liters) of coolant, depending on the specific engine package, radiator size, and whether the truck is equipped with a sleeper cab auxiliary heater. As an ASE-certified master technician, I regularly service heavy-duty cooling systems, and getting the right coolant type and capacity is vital for keeping these Class 8 haulers out on the road and out of the shop.

Quick answer

• Total cooling system capacity: 48–64 quarts (45–60 liters), which equals roughly 12 to 16 US gallons.
• OEM coolant spec: PACCAR Extended Life Coolant (ELC). This is a Nitrite-Free Organic Acid Technology (OAT) coolant, typically red or pink in color. It meets standard heavy-duty specs such as ASTM D6210 and TMC RP 329.
• Mix ratio: 50/50 pre-mixed with deionized water. If using concentrate, you must mix it 50/50 with distilled or deionized water to ensure proper freeze and boil protection.

Capacity by engine option

Because the T680 is a highly customizable Class 8 truck, exact capacities vary based on the frame length, radiator size, and sleeper heating loops. Below are the estimated system capacities for the most common engine configurations. Always check the capacity label under the hood or fill until the surge tank indicates the proper level.

Note: Trucks equipped with large sleeper cabs and dual heater cores will require capacities on the higher end of these ranges.

Flush interval

Heavy-duty ELC formulations are designed to go the distance, but they still require maintenance and testing.

• Normal duty: For a typical over-the-road 2022 Kenworth T680 using Nitrite-Free OAT ELC, the flush interval is typically 600,000 miles, 12,000 operating hours, or 6 years (whichever comes first).
• Severe duty/Maintenance: Even though the fluid lasts a long time, it is highly recommended to test the coolant using proper ELC test strips every 300,000 miles or twice a year. If the system becomes contaminated with regular conventional coolant (IAT), the extended life properties are ruined, and an immediate flush is required.

How to refill & bleed

Modern heavy-duty diesels like the MX-13 and X15 have complex cooling systems with EGR coolers and extensive heater hose routing that easily trap air.

1. Drain the system: Open the petcock at the bottom of the radiator. Remove the surge tank cap to speed up the draining process.
2. Vacuum fill (Recommended): The most reliable way to refill a T680 is using a heavy-duty pneumatic vacuum coolant filler. This pulls a vacuum on the entire cooling system, completely collapsing the hoses, and then sucks the new 50/50 coolant in without introducing any air pockets.
3. Manual fill & bleed: If you do not have a vacuum filler, slowly pour the coolant into the surge tank. Open the air bleed valve located near the top of the EGR cooler or thermostat housing (depending on the engine) to allow trapped air to escape while filling.
4. Run the heaters: Turn the key on and set both the main cab heater and the sleeper cab heater to maximum heat. This opens the heater control valves.
5. Warm up and top off: Start the engine and let it run up to operating temperature until the thermostat opens. Watch the surge tank level closely and top off as the system purges remaining air. Recheck the level after the truck's first loaded trip.

Common cooling system issues

While the 2022 Kenworth T680 is a modern and refined truck, there are a few cooling system quirks technicians look out for:

• Water pump weeping: Keep an eye on the weep hole on the water pump housing. A small amount of dry, crusty pink residue can be normal, but active dripping indicates a failing internal seal.
• EGR cooler leaks: If you are losing coolant but see no external leaks, the EGR cooler may be internally leaking coolant into the exhaust stream. This often presents as white smoke from the stack or a gummy EGR valve.
• Coolant hose clamps: Constant heavy-duty vibrations can cause constant-tension clamps or standard worm-gear clamps to loosen over time, leading to slow leaks at the radiator inlet/outlet.

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