2021 Ford F-350 Super Duty Coolant Capacity & Type

Your 2021 Ford F-350 Super Duty holds approximately 22-26 quarts (20.8-24.6 liters) of coolant in its cooling system, depending on the engine.

Quick Answer

• Total Cooling System Capacity: 22-26 quarts (20.8-24.6 liters)
• OEM Coolant Spec: Ford Yellow Antifreeze/Coolant, Pre-diluted 50/50, or Concentrate, meeting Ford Specification WSS-M97B57-A2 (P-OAT - Phosphated Organic Acid Technology).
• Mix Ratio: 50/50 with distilled water if using concentrate.

Capacity by Engine Option

The 2021 Ford F-350 Super Duty was available with several engine options, each with a slightly different coolant capacity:

• 6.2L V8: Approximately 22-24 quarts (20.8-22.7 liters)
• 7.3L V8: Approximately 22-24 quarts (20.8-22.7 liters)
• 6.7L Power Stroke V8 Diesel: Approximately 24-26 quarts (22.7-24.6 liters)

Always refer to your owner's manual for the most precise capacity for your specific engine configuration.

Flush Interval

Maintaining your cooling system is crucial for the longevity of your engine. Ford recommends the following coolant flush intervals for your 2021 F-350 Super Duty:

• Normal Duty: Replace initially at 10 years or 200,000 miles, then every 5 years or 100,000 miles, whichever comes first.
• Severe Duty (e.g., heavy towing, extreme temperatures, off-road use): Consider more frequent inspections and potentially earlier replacement, typically around 5 years or 100,000 miles.

Regularly check your coolant level and condition between flushes. If the coolant appears discolored or murky, it's time for a flush, regardless of mileage.

How to Refill & Bleed

Refilling and bleeding the cooling system on your F-350 Super Duty is an important process to ensure all air pockets are removed. Here's a general guide:

1. Drain the System: With the engine cool, open the draincock on the bottom of the radiator and remove the radiator cap to allow the coolant to drain completely. Some Super Duty models, particularly those with the 6.7L Power Stroke diesel, may have additional engine block drain plugs – consult your service manual.
2. Close Draincock & Refill: Close the radiator draincock. Begin to slowly add the Ford-specified coolant (50/50 mix) to the coolant degas bottle (reservoir) until it reaches the MAX fill line.
3. Start Engine & Bleed: Start the engine and set the heater to its highest temperature setting with the fan on low. This opens the heater core valve, allowing coolant to circulate through the heater core.
4. Monitor Coolant Level: As the engine warms up, the thermostat will open, and coolant will begin to circulate. The coolant level in the degas bottle may drop as air purges from the system. Continue to add coolant to maintain the MAX fill line.
5. Burp the System: Gently squeeze the upper and lower radiator hoses several times to help release trapped air. You may see bubbles rise in the degas bottle.
6. Drive Cycle & Recheck: Once the engine reaches operating temperature and no more air bubbles are visible, install the cap. Drive the truck for a short period, allow it to cool completely, and then recheck the coolant level in the degas bottle. Top off if necessary.

For 6.7L Power Stroke Diesel models, special attention should be paid to the secondary cooling system (charge air cooler circuit), which has its own degas bottle and may also require bleeding. Some professional shops may utilize a vacuum-fill tool for a more thorough initial fill and bleed, especially on complex systems like the diesel. If an air bleed screw is present on a hose or thermostat housing, open it slightly while filling until coolant emerges, then close it.

Common Cooling System Issues for this Generation

Owners of 2021 Ford F-350 Super Duty trucks may encounter some cooling system-related issues, although largely reliable:

• Degas Bottle Cracks/Leaks: The plastic degas bottle can sometimes develop cracks, leading to slow coolant leaks. Inspect the bottle regularly for hairline cracks or discoloration around seams.
• Water Pump Leaks: While not extremely common for a vehicle of this age, water pump seals can eventually wear, leading to leaks. Look for coolant puddles or residue near the front of the engine.
• Thermostat Issues: A failing thermostat can cause the engine to run too hot or too cold. Symptoms include an overheating engine, slow warm-up, or inconsistent temperature gauge readings.
• Radiator Leaks: Road debris or age can cause damage to the radiator, resulting in leaks. Check for coolant stains on the radiator fins or at the end tanks.
• Coolant Hose Leaks: Hoses can degrade over time, leading to cracks or softened spots that can leak. Regularly inspect all coolant hoses for bulges, cracks, or signs of seepage.

For 6.7L Power Stroke diesel models, specific issues can include problems with the secondary cooling system, including leaks from the charge air cooler system or issues with its dedicated pump.

Find a trusted shop on Repairius.