2018 Peterbilt 579 Coolant Capacity & Type

The 2018 Peterbilt 579's cooling system holds approximately 13.5 gallons (51.1 liters) of coolant, depending on the engine and sleeper configuration.

Quick Answer

• Total Cooling System Capacity: Approximately 13.5 gallons / 51.1 liters for models with the PACCAR MX-13 engine. Capacity may vary slightly based on sleeper configuration and other options.
• OEM Coolant Specification: Peterbilt Extended Life Coolant (ELC). This is a Nitrited Organic Additive Technology (NOAT) coolant, typically red or pink in color. It must meet the TMC RP-329 or RP-338 Type A, and ASTM D6210 standards. The PACCAR specification is CS0185.
• Mix Ratio: 50/50 mix of coolant concentrate and distilled water. Pre-mixed 50/50 solutions are recommended to ensure the proper water quality and concentration for corrosion protection down to -34°F (-37°C).

Capacity by Engine Option

The 2018 Peterbilt 579 was primarily offered with two engine platforms. The cooling system capacity is largely determined by the engine choice.

Note: These values are for the complete system, including the engine, radiator, and heater cores. Actual capacity can vary slightly.

Flush Interval

Following the correct flush and refill interval is critical for preventing corrosion, cavitation, and deposits in the engine and aftertreatment system.

• Normal Service: Peterbilt recommends an initial service life of 750,000 miles (1,200,000 km), 15,000 hours, or 6 years, whichever comes first, when using Peterbilt ELC NOAT.
• Extender Use: To reach the maximum service life, a coolant extender (SCA/supplemental coolant additive) must be added at 300,000 miles (480,000 km) or 6,000 hours. The system should be tested for additive levels at each service interval.
• Severe Duty: For vehicles under severe duty cycles (e.g., heavy hauling, frequent idling, off-highway use), it is recommended to test the coolant quality every 250,000 miles and service as needed.

How to Refill & Bleed

Properly refilling and bleeding the cooling system is essential to prevent airlocks, which can cause overheating and damage to the engine and EGR components.

1. Ensure Safety: Only perform this service when the engine is completely cool. The system is under pressure when hot.
2. Drain System: Open the radiator petcock (drain valve) at the bottom corner of the radiator. Also, remove the engine block drain plug(s) to ensure a complete drain.
3. Flush (If Required): If changing coolant types or if the old coolant is contaminated, flush the system with clean water or a commercial flushing agent designed for heavy-duty diesel engines.
4. Refill Slowly: Close all drain plugs. Slowly fill the system through the expansion tank (surge tank) with a 50/50 premixed NOAT ELC. Filling too quickly can trap air.
5. Bleeding the System: Unlike many passenger cars, these trucks often have vent lines that help purge air automatically. However, it is best practice to:
   • Fill the system until the level in the expansion tank is stable at the "COLD FULL" mark.
   • Start the engine with the heater set to maximum heat and fan speed.
   • Allow the engine to idle and reach operating temperature. You will see the coolant level drop in the expansion tank as the thermostat opens and air is purged.
   • Carefully top off the coolant level in the expansion tank as it drops. Do not exceed the "HOT FULL" mark.
   • Secure the pressure cap and continue to let the engine run for 15-20 minutes to ensure all air is expelled. Check for leaks.
   • Let the engine cool down completely and re-check the coolant level, topping off to the "COLD FULL" line if necessary.

Common Cooling System Issues

The PACCAR MX engines and related cooling systems in the 579 are generally robust, but some issues can arise:

• EGR Cooler Failure: A common failure point on many modern diesel engines. A leaking EGR cooler can introduce coolant into the exhaust or intake, causing white smoke and coolant loss.
• Water Pump Leaks: The water pump seal can fail over time, leading to a slow drip or a steady leak from the weep hole on the pump housing.
• Plastic Tank/Hose Fitting Leaks: The radiator and expansion tank often have plastic components. Over time, heat cycles can cause the plastic to become brittle and crack, especially at hose connections, leading to leaks.
• Thermostat Issues: A thermostat stuck open will cause the engine to take a very long time to warm up, affecting fuel efficiency and emissions systems. A thermostat stuck closed will lead to rapid overheating.
• Clogged Radiator Fins: External debris (bugs, dirt, etc.) can clog the radiator fins, reducing airflow and cooling efficiency, especially under heavy load.

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