2022 GMC Sierra 2500HD Coolant Capacity, Type, and Maintenance Guide

The 2022 GMC Sierra 2500HD holds between 16.8 quarts (15.9 liters) and 30.9 quarts (29.2 liters) of coolant, depending on whether it is equipped with the 6.6L gas V8 or the 6.6L Duramax turbo-diesel engine. As an ASE-certified master technician, I regularly service these heavy-duty trucks, and maintaining the complex thermal management systems on modern HD pickups is critical for transmission, engine, and towing performance.

Below is your comprehensive guide to the coolant capacity, factory specifications, and maintenance procedures for the 2022 GMC Sierra 2500HD.

Quick answer

• Total cooling system capacity: 16.8 quarts (15.9 L) to 30.9 quarts (29.2 L), depending on the engine.
• OEM coolant spec: Dex-Cool (Orange), OAT (Organic Acid Technology), GM Spec GMW3420.
• Mix ratio: 50/50 mixture of Dex-Cool concentrate and clean, drinkable water (preferably distilled or deionized), or use a 50/50 pre-mixed solution.

Capacity by engine option

Because the 2022 GMC Sierra 2500HD is offered with two vastly different powertrains, the cooling system capacities vary significantly. The Duramax diesel requires a massive amount of coolant to support its primary cooling system, charge air cooler loop, and heavy-duty transmission cooler.

Note: Capacities are approximate and reflect a completely dry system. A standard drain and fill will require slightly less fluid, as some coolant always remains in the heater core and engine block.

Flush interval

General Motors specifies a distinct maintenance schedule for the 2022 Sierra 2500HD's cooling system to ensure the OAT additives do not degrade and cause internal corrosion.

• Normal Duty: Flush and replace the Dex-Cool coolant every 150,000 miles or 5 years, whichever comes first.
• Severe Duty: If you frequently tow heavy trailers, idle for extended periods, or operate in extreme heat or dusty conditions, it is highly recommended to inspect and test the coolant regularly. Many technicians recommend dropping the flush interval to 75,000 to 100,000 miles for severe service vehicles to protect the water pump and EGR cooler (on diesel models).

How to refill & bleed

Modern HD trucks have complex cooling circuits, especially the L5P Duramax, which utilizes multiple radiators and cooling loops. Air pockets can cause localized overheating or prevent the heater core from working properly.

1. Drain the system: Locate the radiator drain petcock at the bottom corner of the radiator. Open it and allow the old coolant to drain completely into an appropriate catch pan.
2. Vacuum Fill (Highly Recommended): Due to the complexity of the Sierra's cooling system, using a pneumatic vacuum coolant filler (like an Airlift tool) is the factory-approved and most reliable method. This tool pulls the entire system into a deep vacuum, checking for leaks, and then draws the 50/50 Dex-Cool mixture into every crevice without introducing air.
3. Manual Bleed (If vacuum fill is unavailable): Fill the surge tank slowly to the "Cold Fill" line. Leave the cap off.
4. Start the engine and turn the cabin heater to its maximum heat setting with the blower on low.
5. Allow the engine to idle and reach normal operating temperature so the thermostat opens. You will see the fluid level drop in the surge tank.
6. Top off the surge tank as the level drops. Gently squeeze the upper radiator hose to help force trapped air out into the surge tank.
7. Once the level stabilizes and hot air blows from the cabin vents, install the pressure cap. Test drive the vehicle and recheck the level after the engine has completely cooled down.

Common cooling system issues

While the 2022 GMC Sierra 2500HD is generally robust, this generation has a few cooling system quirks to watch out for as the mileage climbs:

• Water Pump Weep Hole Leaks: On the 6.6L Duramax (L5P), the water pump can occasionally develop slow leaks from the weep hole. If you smell sweet coolant but don't see a puddle, check the bottom of the water pump housing.
• Radiator End Tank Crimp Leaks: The factory radiators use an aluminum core crimped to plastic end tanks. Over thousands of thermal cycles, these crimps can fatigue and weep coolant down the sides of the radiator.
• EGR Cooler Leaks (Diesel): While improved over older generations, the EGR cooler on the L5P can still fail internally over time, leading to mysterious coolant loss without external puddles.
• Surge Tank Cracking: The plastic coolant surge tank is subjected to immense heat under the hood and can become brittle, leading to hairline cracks along the seams.

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