2018 GMC Sierra 1500 Coolant Capacity & Type

The 2018 GMC Sierra 1500 has a total cooling system capacity that ranges from 13.1 to 17.4 quarts (12.4 to 16.5 liters), depending on the engine option.

Quick Answer

• Total Cooling System Capacity: 13.1 to 17.4 quarts (12.4 to 16.5 liters)
• OEM Coolant Specification: ACDelco GM OE Dex-Cool Antifreeze/Coolant (Orange, OAT Chemistry, GM 6277M)
• Mix Ratio: 50/50 with deionized water (Pre-mixed options are recommended)

Capacity by Engine Option

The specific capacity of your truck's cooling system will depend on which engine it is equipped with.

Flush Interval

Following the factory-recommended service interval is crucial for maintaining the health of your engine's cooling system.

• Normal Service: The factory schedule recommends a coolant flush and replacement every 5 years or 150,000 miles, whichever comes first.
• Severe Duty: If the vehicle is used for frequent towing, heavy hauling, extensive idling, or operating in extreme temperatures, consider shortening this interval to every 60,000-75,000 miles to prevent premature coolant breakdown.

How to Refill & Bleed

Properly refilling and bleeding the air from the cooling system is critical to prevent overheating. While a DIY top-off is simple, a full flush and fill can be complex.

1. Ensure the Engine is Cool: Never open a hot cooling system.
2. Mix Coolant: If using concentrate, mix it 50/50 with deionized water before adding.
3. Fill Slowly: Add the coolant mixture to the coolant recovery tank (degas bottle), not the radiator cap.
4. Bleeding Procedure: These trucks do not have a traditional radiator cap or manual air-bleed screws. The system is designed to be self-bleeding, but air pockets can be stubborn. A spill-free funnel attached to the recovery tank can help purge air as the engine runs and the thermostat opens. For best results, especially after a major component replacement, a vacuum-fill tool is highly recommended by technicians to ensure no air is trapped in the system.

Common Cooling System Issues

This generation of Sierra/Silverado trucks (2014-2018) has a few known issues to watch for:

• Water Pump Failure: The original equipment water pump can be a failure point. Symptoms include a coolant leak from the front of the engine (weep hole), a grinding or whining noise, or a sudden spike in engine temperature.
• Thermostat Issues: A thermostat stuck open will cause the engine to be slow to warm up and may trigger a check engine light (P0128). A thermostat stuck closed will cause rapid overheating.
• Coolant Leak at Hoses/Fittings: Over time, plastic fittings and hose clamps can become brittle or weak, leading to leaks. The heater core hoses and their quick-connect fittings are common culprits.
• Radiator Leaks: While less common than on older models, leaks can develop at the seams where the plastic end tanks are crimped to the aluminum core.

If you're experiencing any of these issues or are unsure about performing a coolant service yourself, find a trusted shop on Repairius.