2025 GMC Sierra 1500 Coolant Capacity & Type Guide

The 2025 GMC Sierra 1500 holds between 11.5 and 16.5 quarts (10.9 to 15.6 liters) of coolant, depending on the specific engine and optional heavy-duty cooling packages equipped. As an ASE-certified master technician, I regularly service the modern GM truck lineup, and keeping the cooling system in top shape is critical for both towing performance and engine longevity. Below is your comprehensive guide to the coolant requirements, specifications, and maintenance procedures for the 2025 GMC Sierra 1500.

Quick answer

When it comes to servicing the cooling system on your 2025 Sierra 1500, here are the essential specifications you need to know before starting the job:

• Total cooling system capacity: 11.5 to 16.5 quarts (10.9 to 15.6 liters), varying by engine and towing packages.
• OEM coolant spec: ACDelco Dex-Cool (Orange), which is an OAT (Organic Acid Technology) coolant meeting GM specification GMW3420.
• Mix ratio: 50/50 mixture of clean, drinkable water (preferably distilled) and Dex-Cool concentrate, or use a 50/50 pre-mixed Dex-Cool solution.

Capacity by engine option

Because the 2025 GMC Sierra 1500 is offered with a diverse powertrain lineup—including a turbocharged four-cylinder, traditional V8s, and an inline-six diesel—the coolant capacity varies significantly. Always check your owner's manual or RPO codes for heavy-duty cooling packages (like the Max Trailering Package), which increase system volume.

Note: Capacities are approximate. When performing a drain and fill, you will rarely remove the entire dry-fill capacity from the system.

Flush interval

GM recommends specific intervals to ensure the Dex-Cool OAT coolant retains its anti-corrosive properties and effectively regulates engine temperatures.

• Normal Duty: Flush and replace the coolant every 150,000 miles or 5 years, whichever comes first.
• Severe Duty: If you frequently tow heavy loads, drive in extreme heat, idle extensively, or drive in dusty off-road conditions, it is highly recommended to inspect the coolant annually and perform a flush closer to the 100,000-mile or 4-year mark to prevent internal corrosion and water pump wear.

How to refill & bleed

Modern GM trucks feature complex cooling networks, especially those with auxiliary coolers and turbocharged engines. Proper bleeding is mandatory to prevent localized overheating.

1. Drain the system: Wait until the engine is completely cold. Open the radiator petcock (if equipped) or remove the lower radiator hose to drain the old coolant.
2. Vacuum fill (Recommended): The most effective way to refill a 2025 Sierra 1500 is by using a pneumatic vacuum coolant filler. This tool pulls a vacuum on the empty system, checks for leaks, and draws the new 50/50 Dex-Cool mixture in without introducing air pockets.
3. Manual fill (If vacuum tool is unavailable): Slowly pour the 50/50 Dex-Cool mix into the coolant surge tank until it reaches the cold fill line.
4. Bleed the air: Leave the surge tank cap off. Start the engine and turn the cabin heater to its maximum temperature setting with a low fan speed. Let the engine idle until it reaches operating temperature and the thermostat opens (the upper radiator hose will become hot).
5. Top off: As air burps out of the system, the coolant level in the surge tank will drop. Add coolant to maintain the level at the cold fill line. Once the level stabilizes and hot air blows from the cabin vents, install the cap tightly. Recheck the level after your next few drive cycles.

Common cooling system issues

While the 2025 GMC Sierra 1500 is a robust truck, there are a few cooling system quirks common to this generation of GM pickups:

• Water pump leaks on V8s: The 5.3L and 6.2L engines have historically been prone to weeping water pumps as mileage increases. Keep an eye out for a sweet smell or orange crust around the water pump weep hole.
• Radiator baffle and end tank leaks: The crimped plastic end tanks on the factory aluminum radiators can occasionally develop micro-cracks or seal leaks under heavy towing stress.
• Air pockets in the 3.0L Duramax: The diesel engine utilizes a complex split-cooling system. If not vacuum-filled properly, trapped air can cause erratic temperature gauge readings or poor heater performance.

If you suspect a leak or need assistance performing a full system flush on your truck, don't leave it to chance. Find a trusted shop on Repairius.