2020 Peterbilt 579 Coolant Capacity and Type

The 2020 Peterbilt 579's cooling system holds approximately 13-14 gallons (49.2-53.0 liters) of coolant, depending on the engine and sleeper configuration.

Quick Answer

• Total Cooling System Capacity: 13-14 gallons (49.2-53.0 liters)
• OEM Coolant Specification: Red or Pink Extended Life Coolant (ELC), Nitrite-Free Organic Acid Technology (OAT). Look for coolants meeting Cummins CES 14603 or PACCAR specifications.
• Mix Ratio: 50/50 mix of coolant concentrate and distilled water. Pre-mixed 50/50 solutions are recommended.

Capacity by Engine Option

The 2020 Peterbilt 579 was offered with two engine options, the PACCAR MX-13 and the Cummins X15. While the core cooling system is similar, capacities can vary slightly based on ancillary equipment and sleeper configuration (e.g., presence of a cab heater or bunk heater).

Note: These are estimates for a standard day cab configuration. Sleeper models with auxiliary heaters may hold slightly more. Always confirm with your owner's manual or a certified technician.

Flush Interval

Regular coolant flushes are critical for preventing corrosion, cavitation, and deposits in a heavy-duty diesel engine.

• Normal Duty: Peterbilt recommends an initial coolant flush at 600,000 miles (965,000 km) or 6 years. Subsequent flushes should occur every 300,000 miles (480,000 km) or 3 years, whichever comes first.
• Severe Duty: For vehicles under heavy loads, frequent idling, or operating in extreme temperatures, consider shortening the flush interval to every 400,000 miles (640,000 km) or 4 years.

How to Refill & Bleed

Properly refilling and bleeding the cooling system is essential to prevent air pockets, which can lead to overheating and engine damage.

1. Drain: Ensure the engine is cool. Open the radiator petcock and any block drains to completely empty the system.
2. Refill: Use a 50/50 mixture of ELC and distilled water. Fill the system slowly through the expansion tank (surge tank) to the "MAX" cold line.
3. Bleed: The Peterbilt 579 cooling system is designed to be self-bleeding. However, it is best practice to run the engine with the heater on high and the expansion tank cap loose for 15-20 minutes to purge any trapped air. Some technicians prefer using a vacuum-fill tool to ensure a complete, air-free fill, which is highly recommended for these large-capacity systems.
4. Top Off: After the engine has cooled completely, re-check the coolant level in the expansion tank and top off as necessary.

Common Cooling System Issues

While generally robust, the 2020 Peterbilt 579 can experience several common cooling system issues:

• EGR Cooler Failure: The Exhaust Gas Recirculation (EGR) cooler is a known weak point. A failing EGR cooler can leak coolant into the exhaust, causing white smoke and significant coolant loss.
• Radiator and Hose Leaks: Given the high mileage and constant vibration these trucks endure, rubber hoses can degrade and plastic radiator end tanks can develop cracks. Regular inspection of all hoses, clamps, and the radiator itself is crucial.
• Water Pump Failure: The water pump is a wear-and-tear item. Symptoms of failure include coolant leaking from the pump's weep hole, a grinding noise from the front of the engine, or an overheating condition.
• Thermostat Issues: A thermostat stuck open will cause the engine to take a long time to reach operating temperature, while a thermostat stuck closed will lead to rapid overheating.

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