2022 Peterbilt 579 Coolant Capacity & Type Guide

The 2022 Peterbilt 579 holds approximately 44 to 58 quarts (11 to 14.5 gallons or 41.6 to 54.8 liters) of coolant, heavily depending on your specific engine choice, radiator size, and whether the truck is equipped with a sleeper cab heater loop. As an ASE-certified master technician dealing with heavy-duty platforms, I always emphasize that getting the coolant chemistry right on these modern emissions-equipped diesels is just as critical as maintaining the correct fluid level.

Quick answer

• Total Cooling System Capacity: 44 to 58 quarts (41.6 to 54.8 liters) / 11 to 14.5 gallons, varying by engine and sleeper configuration.
• OEM Coolant Spec: TRP Extended Life Coolant (ELC) or equivalent Nitrite-Free OAT (Organic Acid Technology). Look for PACCAR ELC specifications or Cummins CES 14603/14636.
• Coolant Color: Red / Magenta.
• Mix Ratio: 50/50 pre-mixed with distilled water (for extreme sub-zero climates, up to a 60/40 coolant-to-water ratio may be used, but never exceed 60%).

Capacity by engine option

The 2022 Peterbilt 579 is generally spec'd with either PACCAR or Cummins powerplants. Keep in mind that trucks with large sleeper cabs and auxiliary APU heating loops will require the higher end of these capacity ranges.

Note: Always buy 1-2 extra gallons when doing a complete flush to account for sleeper loops and APU lines.

Flush interval

Modern heavy-duty Extended Life Coolant (ELC) is incredibly robust, but it still has a finite lifespan, especially when subjected to the intense heat of modern EGR systems.

• Normal Duty: Replace the coolant every 600,000 miles, 12,000 operating hours, or 6 years (whichever comes first). If utilizing an ELC extender package at 500,000 miles, this can sometimes be pushed to 1,000,000 miles depending on fleet maintenance protocols and regular coolant testing.
• Severe Duty (High Idle / Vocational): Flush and replace every 400,000 miles, 8,000 hours, or 4 years. Regular test strips should be used every 25,000 miles to check for proper freeze point, pH levels, and carboxylate (inhibitor) levels.

How to refill & bleed

Air pockets in modern heavy-duty diesels can cause localized boiling, leading to catastrophic EGR cooler or cylinder head failure.

1. Drain the System: Open the radiator petcock and remove the lower block drain plug. If equipped, ensure the sleeper heater control valve is open so the rear loop drains.
2. Vacuum Fill (Highly Recommended): Because of the long coolant lines running to the sleeper cab and the complex routing of the EGR cooler, using a pneumatic vacuum coolant filler is strongly advised. This pulls the system into a deep vacuum, checking for leaks, and draws the new 50/50 ELC in without creating air pockets.
3. Manual Fill (If vacuum isn't available): Slowly pour coolant into the surge tank. Locate and open the highest bleed screw on the engine (often near the thermostat housing or EGR cooler) until a steady stream of fluid escapes.
4. Warm Up & Top Off: Start the engine and turn all cab and sleeper heaters to their maximum heat setting. Run the truck at a high idle (approx. 1,000 RPM) until the thermostat opens (the upper radiator hose will become hot).
5. Final Check: Shut the engine down, allow it to cool, and top off the surge tank to the "COLD MAX" line.

Common cooling system issues

For the 2022 Peterbilt 579 generation, operators and technicians should keep an eye out for a few specific cooling system quirks:

• EGR Cooler Leaks: Both the PACCAR and Cummins engines route incredibly hot exhaust gases through the EGR cooler. A drop in coolant level with no visible external leak is often the first sign of an internally ruptured EGR cooler.
• Water Pump Weep Hole Leaks: Small amounts of dried red crust around the water pump weep hole are normal, but active dripping indicates the internal mechanical seal has failed and the pump requires replacement.
• Coolant Level Sensor Failures: The sensor inside the surge tank can occasionally fail or become coated in scaling if poor-quality tap water was used in an emergency. This will trigger a low coolant warning light and potentially derate the engine, even if the tank is full.
• Sleeper Heater Valve Sticking: The electronic valve controlling coolant flow to the sleeper cab heater core can get stuck closed, resulting in a lack of heat for the driver and difficulty bleeding the rear coolant loop.

Heavy-duty cooling systems are complex and require professional care to prevent expensive downtime. Find a trusted shop on Repairius.