2023 GMC Sierra 2500HD: Coolant Capacity and Type

The 2023 GMC Sierra 2500HD holds between 15.1 and 24.4 quarts (14.3 and 23.1 liters) of coolant, depending on the engine.

Quick Answer

• Total Cooling System Capacity: 15.1 to 24.4 quarts (14.3 to 23.1 liters)
• OEM Coolant Specification: ACDelco DEX-COOL® (Orange, OAT Chemistry, GM 6277M)
• Mix Ratio: 50/50 with deionized water (pre-mixed is recommended)

Capacity by Engine Option

The 2023 Sierra HD offers two distinct engines, each with its own cooling system capacity.

Flush Interval

Following the factory-recommended flush interval is crucial for protecting the engine from corrosion and overheating.

• Normal Service: The factory fill of DEX-COOL coolant is designed to last for up to 5 years or 150,000 miles (whichever comes first).
• Severe Service: If the truck is frequently used for towing heavy loads, idling for long periods, or operated in extreme temperatures, it's wise to consider a shorter interval, such as every 60,000 to 100,000 miles, to ensure maximum cooling system protection.

How to Refill & Bleed

Topping off or refilling the cooling system on the Sierra HD requires careful attention to avoid air pockets, which can cause overheating.

1. Ensure the Engine is Cold: Never open a hot cooling system. Park on a level surface.
2. Mix Coolant: If using concentrate, mix it 50/50 with deionized water in a clean container before pouring.
3. Fill Slowly: Add the coolant mixture to the coolant reservoir (deaeration tank). Do not fill directly into the radiator.
4. Bleeding Procedure: These trucks are designed to be self-bleeding to an extent, but air pockets can still be stubborn. After filling the reservoir to the "Full Cold" line, start the engine with the reservoir cap off. Let it run for several minutes, watching for the coolant level to drop as air purges. Add coolant as needed to maintain the level.
5. Professional Tip: Many technicians prefer using a vacuum-fill tool on modern trucks like the Sierra HD. This tool pulls the entire cooling system into a deep vacuum, removing all air before drawing the new coolant in, guaranteeing an air-free fill.

Common Cooling System Issues

The 2020-present generation of GMC Sierra HD trucks has proven to be robust. However, some potential issues to watch for include:

• Water Pump Failure: While not widespread, some owners have reported premature water pump leaks. Symptoms include a visible coolant drip from the front of the engine, a low coolant warning, or a whining noise.
• Thermostat Issues: A thermostat stuck open or closed can cause the engine to either overheat or fail to reach operating temperature, triggering a check engine light.
• Radiator Leaks: Damage from road debris can cause leaks in the radiator or condenser. Regular visual inspections can help catch these early.

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