2015 Peterbilt 579 Coolant Capacity & Type

Quick answer

The 2015 Peterbilt 579 total cooling system capacity is between 12 and 14 gallons (45.4 and 53 liters), depending on the engine and sleeper configuration.

• Total Cooling System Capacity: 12–14 gal (45.4–53 L)
• OEM Coolant Specification: Red/Pink Extended Life Coolant (ELC) meeting TMC RP-329 or RP-338 specifications. This is a Nitrited Organic Additive Technology (NOAT) coolant.
• Mix Ratio: 50/50 mix of coolant concentrate and distilled water. Pre-mixed 50/50 is recommended.

Capacity by engine option

Note: Capacity varies based on factors like sleeper configuration, optional auxiliary heaters, and specific radiator size.

Flush interval

• Normal Duty: The recommended service interval for Peterbilt ELC (NOAT) is up to 600,000 miles (965,000 km), 12,000 hours, or 6 years, whichever comes first. An extender should be added at 300,000 miles (480,000 km) or 6,000 hours.
• Severe Duty: More frequent testing and inspection are recommended. Test the coolant’s freeze point and additive levels at least twice per year. Follow the same mileage-based intervals but be prepared to flush sooner if the coolant fails testing.

How to refill & bleed

Refilling and bleeding the cooling system on a 2015 Peterbilt 579, especially with the large PACCAR or Cummins engines, requires care to avoid airlocks. A vacuum-fill tool is highly recommended for a complete and air-free fill.

1. Drain: Ensure the engine is cool. Open the petcock at the bottom of the radiator to drain the system. Disconnecting the lower radiator hose may be necessary for a faster drain.
2. Flush (if required): If changing coolant types or if the old coolant is contaminated, flush the system with distilled water or a commercial flush product until it runs clear.
3. Refill (Vacuum Method Recommended):
   • Attach a vacuum-fill tool to the coolant surge tank (deaeration tank).
   • Draw a vacuum on the cooling system (typically 25-27 inHg).
   • Close the valve to the vacuum pump and ensure the system holds vacuum, indicating no leaks.
   • Submerge the tool's fill hose in your new 50/50 coolant mix and open the valve to allow the vacuum to draw coolant into the system.
4. Bleed: If not using a vacuum-filler, fill the system slowly through the surge tank. Start the engine with the heater on high and let it run until it reaches operating temperature, allowing the thermostat to open. This will help purge any remaining air. Top off the surge tank as the level drops. Be sure to leave appropriate room for expansion as specified on the tank.

Common cooling system issues

• EGR Cooler Failure: A common issue on this generation of heavy-duty trucks. A failing EGR cooler can leak coolant into the exhaust or intake system, leading to white smoke, coolant loss, and potential engine damage if not addressed.
• Radiator and Hose Leaks: Given the high mileage and constant vibration, leaks at hose connections, clamps, and the radiator itself (especially around the end tanks) are a frequent point of failure.
• Surge Tank Cracks: The plastic coolant surge tank can become brittle over time due to heat cycles and may develop cracks, leading to slow leaks and pressure loss.
• Water Pump Failure: The water pump is a wear item. Signs of failure include coolant leaking from the weep hole on the pump or a grinding noise from the pump bearing.

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