2020 CT6 3.6L Coolant Flush - What type of coolant and interval?

ClearTheCode admin answer:

Proactive coolant maintenance is excellent for the longevity of your 2020 Cadillac CT6's engine. At 50,000 miles, you're approaching the general recommendation for your first major coolant service.

Coolant Type and Interval:

• Your 2020 Cadillac CT6 with the 3.6L V6 engine requires DEX-COOL® Extended Life Coolant. It's an orange/reddish-orange OAT (Organic Acid Technology) coolant. Using any other type can lead to corrosion, clumping, and damage to your cooling system components.
• The typical service interval for DEX-COOL in modern GM vehicles like your CT6 is 5 years or 150,000 miles, whichever comes first. While 50,000 miles is well within the mileage, you're nearing the 5-year mark if you bought it new in 2020. It's a good idea to inspect the coolant for clarity and debris, and consider a flush if it looks discolored.

Causes for Coolant Degradation:

• Additive Depletion: Over time, the corrosion inhibitors and other additives in the coolant deplete, reducing its ability to protect engine components.
• Contamination: Rust, scale, and other debris can accumulate, leading to blockages and reduced cooling efficiency.
• pH Change: The coolant's pH can become acidic, accelerating corrosion.

Recommended Action Steps:

1. Inspect Coolant: Visually check the coolant in the reservoir when the engine is cold. It should be clear and orange. If it's murky, brown, or contains particles, a flush is definitely warranted.
2. Drain and Fill/Flush: For a DIY, a simple drain and fill from the radiator petcock will replace a good portion of the old coolant. For a more thorough job, a full flush involves running distilled water through the system until clear, then refilling with a 50/50 DEX-COOL and distilled water mixture. Ensure the heater is on full hot during the process.
3. Bleeding the System: The CT6, like many modern cars, is largely self-bleeding through the expansion tank. However, after refilling, run the engine with the heater on, allowing it to reach operating temperature. Monitor the coolant level in the reservoir and top off as needed after the engine cools down. Some models have bleed screws, but often the expansion tank handles it.
4. Check for OBD Codes: While old coolant doesn't directly trigger codes, issues like low coolant or overheating could lead to codes like P0117 (Engine Coolant Temperature Sensor Low) or P0118 (ECT Sensor High).

When to See a Shop:

• Lack of Experience: If you're uncomfortable working with hot fluids or don't have the proper disposal methods for old coolant.
• Persistent Air Pockets: If you're having trouble bleeding the system and the engine is running hot after the service.
• Suspected Leaks or System Issues: If you notice any leaks, or if the coolant looks particularly sludgy, indicating a potential head gasket issue or other serious problem.