2021 GMC Sierra 1500 Coolant Capacity & Type

The 2021 GMC Sierra 1500 cooling system typically holds around 16 quarts (15.1 liters) of a specific Dex-Cool Original Equipment Manufacturer (OEM) coolant.

Quick Answer

• Total Cooling System Capacity: Approximately 16 quarts (15.1 liters)
• OEM Coolant Spec: Dex-Cool (Orange/Reddish-Orange, OAT - Organic Acid Technology, GM Dex-Cool specification)
• Mix Ratio: 50/50 prediluted or concentrate mixed with distilled water

Capacity by Engine Option

While the 16-quart capacity is a general guideline for many engine options, slight variations may occur. Always consult your owner's manual for the precise capacity for your specific engine configuration. The 2021 GMC Sierra 1500 offered several engine choices, including:

Flush Interval

Normal Duty: For most driving conditions, the cooling system in your 2021 GMC Sierra 1500, when using Dex-Cool coolant, has a long-life expectancy. The recommended flush interval is typically 5 years or 150,000 miles, whichever comes first.

Severe Duty: If your vehicle experiences severe operating conditions, such as frequent towing, hauling heavy loads, extreme temperatures, or extensive idling, it's advisable to consider a more frequent inspection and potentially a flush. While not always a reduced flush interval, careful monitoring of coolant condition is recommended.

How to Refill & Bleed

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

Steps:

1. Safety First: Ensure the engine is completely cool before starting. Wear appropriate personal protective equipment (PPE).
2. Drain Old Coolant (if flushing): Open the radiator drain petcock and/or lower radiator hose to drain the old coolant into a suitable container for proper disposal.
3. Flush (if necessary): If performing a flush, follow product instructions carefully. Often involves flushing with distilled water until clear.
4. Close Drain Points: Once draining/flushing is complete, close the radiator petcock and secure the lower radiator hose.
5. Refill: Slowly add the recommended 50/50 prediluted Dex-Cool coolant to the radiator. Fill until it reaches the cold fill line in the coolant reservoir.
6. Bleed Air:
   • Leave the radiator cap off. Start the engine and let it run with the heater on full blast (this opens the heater core allowing coolant to circulate through it).
   • Monitor the coolant level in the radiator and reservoir. As the engine warms up, the thermostat will open, and coolant will begin to circulate. You may see air bubbles escape from the radiator opening. Top off coolant as needed.
   • Some 2021 GMC Sierra 1500 models (especially with certain engine configurations) may have bleed screws located on or near the thermostat housing or upper radiator hose. If present, open these bleed screws slightly to allow trapped air to escape until a steady stream of coolant emerges, then close them.
   • Squeeze the upper and lower radiator hoses occasionally to help dislodge air pockets.
   • Continue this process until no more air bubbles appear, and the coolant level stabilizes. Install the radiator cap.
7. Final Check: After a test drive, allow the engine to cool completely and recheck the coolant level in the reservoir. Adjust as necessary.

Vacuum Fill Note: For the most thorough and efficient air removal, especially after a complete system drain or component replacement, a vacuum-fill tool is highly recommended. This tool evacuates all air from the system before refilling, virtually eliminating air pockets.

Common Cooling System Issues for this Generation

Owners of the 2021 GMC Sierra 1500 (and similar generation GM trucks) may encounter certain cooling system-related issues:

• Water Pump Leaks: While not universally rampant, water pump failures and associated leaks can occur. Keep an eye out for coolant puddles under the front of the vehicle or a drop in coolant levels.
• Thermostat Issues: Stuck open or closed thermostats can lead to slow engine warm-up (stuck open) or overheating (stuck closed). Modern thermostats are often electronically controlled, and failures can trigger "check engine" lights.
• Radiator/Hose Leaks: Over time, hoses can degrade and develop leaks, and radiators can suffer from damage or corrosion, leading to coolant loss. Regularly inspect hoses for cracks or swelling.
• Coolant Temperature Sensor Failures: A faulty coolant temperature sensor can send incorrect readings to the engine control module, leading to inaccurate temperature gauge readings or poor engine performance.
• GMC Dex-Cool Compatibility: While Dex-Cool is a good coolant, it