2018 Kenworth T680 Coolant Capacity & Type

The 2018 Kenworth T680 typically holds between 70 to 80 quarts (17.5 to 20 gallons or approximately 66 to 76 liters) of coolant, depending on the specific engine and cooling system configuration.

Quick Answer

• Total Cooling System Capacity: 70–80 quarts (66–76 Liters)
• OEM Coolant Spec: PACCAR (PN PC50041 or PC50042) or Cummins (PN CC2853235, CC2853236, or CC2853237) — typically an OAT (Organic Acid Technology) or HOAT (Hybrid Organic Acid Technology) ELC (Extended Life Coolant). Always refer to the engine manufacturer's specifications. It is commonly red, pink, or purple.
• Mix Ratio: 50/50 pre-mix, or 50% concentrate with 50% distilled water.

Capacity by Engine Option

The Kenworth T680 in 2018 was commonly equipped with PACCAR MX-13 or Cummins X15 engines. The exact coolant capacity can vary slightly based on the installed engine and optional equipment such as auxiliary heaters or larger radiators.

Flush Interval

Maintaining the coolant flush interval is critical for preventing cooling system issues and ensuring the longevity of your engine. Most heavy-duty trucks, including the 2018 Kenworth T680, follow these guidelines:

• Normal Duty: 300,000 to 600,000 miles, 4,800 to 9,600 operating hours, or 3 to 6 years, whichever comes first. Refer to your engine's specific maintenance manual for exact intervals.
• Severe Duty: If operating under severe conditions (e.g., extreme temperatures, heavy loads, frequent idling, dusty environments), it is advisable to inspect and potentially flush the system more frequently, potentially at the lower end of the normal duty range.

Regular testing of the coolant (pH, freeze point, and SCA/DCA levels for conventional coolants, though less common with ELC) is recommended to determine its condition.

How to Refill & Bleed

Properly refilling and bleeding the cooling system after a drain or flush is crucial to prevent air pockets, which can lead to overheating. For the 2018 Kenworth T680, follow these general steps:

1. Drain the System: With the engine cool, open the petcock on the bottom of the radiator and any engine block drain plugs to fully drain the old coolant.
2. Flush (if necessary): If flushing, close the drains, fill with distilled water and a cooling system cleaner (if recommended), run the engine to operating temperature with the heater on, then drain again. Repeat with plain distilled water until the water runs clear.
3. Refill: Close all drain plugs. Slowly fill the cooling system through the surge tank or fill neck with the correct 50/50 coolant mixture. It's often beneficial to have the front of the truck slightly elevated to help trapped air escape.
4. Bleed Air: Start the engine and run it with the heater on high. Leave the surge tank cap off. As the engine warms up, the thermostat will open, and coolant will circulate. Squeeze the upper and lower radiator hoses to help dislodge air bubbles. Look for an air bleed line near the top of the radiator or near the thermostat housing; ensure it's clear and allowing air to escape. Some systems may have dedicated bleed screws – open these until a steady stream of coolant emerges, then close.
5. Monitor Level: Continuously monitor the coolant level in the surge tank and top off as needed until the level stabilizes. Once the engine reaches operating temperature and no more air bubbles appear, replace the surge tank cap.
6. Post-Procedure Check: Drive the truck and then let it cool completely. Recheck the coolant level in the surge tank and add coolant if necessary. Monitor the temperature gauge closely during the first few drives.

For systems with persistent air pockets, a vacuum fill tool can be highly effective at removing air during the refill process.

Common Cooling System Issues

While the Kenworth T680 is a robust truck, certain cooling system issues can arise, especially with age and high mileage:

• Coolant Leaks: Common areas for leaks include radiator hoses, heater hoses, the radiator itself (especially plastic end tanks), water pump seals, and EGR cooler components. PACCAR MX-13 and Cummins X15 engines can also develop leaks around sensors or coolant passages.
• EGR Cooler Failures: The Exhaust Gas Recirculation (EGR) cooler is a known failure point in many modern diesel engines, including those in the T680. A failing EGR cooler can introduce coolant into the exhaust or combustion chamber, leading to white smoke, coolant consumption, and potential engine damage.
• Radiator/Charge Air Cooler (CAC) Blockage: External blockage of the radiator and CAC fins from dirt, debris, bugs, and road grime can restrict airflow and lead to overheating.
• Thermostat Issues: A stuck-open thermostat can cause the engine to run too cool, leading to reduced efficiency and potential DPF regeneration issues. A stuck-closed thermostat can cause severe overheating.
• Water Pump Failure: Bearing failure or seal leakage in the water pump can lead to overheating or coolant loss.
• Fan Clutch Issues: A malfunctioning fan clutch (not engaging when needed) will result in insufficient cooling airflow, leading to overheating, particularly at low speeds or while idling.

Regular inspection of the cooling system components, along with adherence to recommended maintenance schedules, can significantly mitigate these issues.

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