2023 Chevrolet Silverado 3500HD — Coolant Capacity & Type

The 2023 Chevrolet Silverado 3500HD holds about 15–18 quarts (14.2–17.0 liters) of coolant with the 6.6L gas V8, and roughly 26–30 quarts (24.6–28.4 liters) with the 6.6L Duramax diesel.

Quick answer

• Total cooling system capacity (approx.):
  • 6.6L Gas (L8T): 15–18 qt (14.2–17.0 L)
  • 6.6L Duramax Diesel (L5P): 26–30 qt (24.6–28.4 L)
• OEM coolant spec: GM Genuine/ACDelco DEX‑COOL Extended Life, orange, OAT chemistry; meets GM GMW3420 (supersedes GM 6277M)
• Mix ratio: 50/50 coolant and distilled water (or use GM/ACDelco pre‑mix). Up to 60/40 for extreme cold; do not exceed 70% coolant.

Capacity by engine option

Notes:

• Variations depend on cab/box configuration, dual batteries/coolers, and how thoroughly the system is drained (radiator only vs. full block and heater core).
• Always verify level on a cold engine and top off as needed after a few heat cycles.

Flush interval

• Normal service: Replace DEX‑COOL every 5 years or 150,000 miles (240,000 km), whichever comes first.
• Severe service (heavy towing, extended idling, dusty/off‑road): Inspect coolant level/condition at each oil change; replace at 5 years/100,000–150,000 miles depending on condition and usage. Test freeze/boil protection and pH annually.

How to refill & bleed

1. Drain safely: With the engine cold, open the radiator drain cock and remove the surge tank cap. For a fuller drain, remove the lower radiator hose; on diesel, expect a large volume—use multiple drain pans.
2. Close drains and connect hoses. If switching coolant types, flush with distilled water until clear.
3. Refill through the surge/degassing tank:
   • Preferred: Vacuum‑fill the system to avoid air pockets (especially recommended on the L5P diesel due to system size and long hose runs).
   • Gravity fill: Add 50/50 DEX‑COOL slowly to the COLD FILL line. Let it settle; squeeze the upper radiator hose to burp air.
4. Initial warm‑up bleed: Set HVAC to full hot. Start engine and idle. As the thermostat opens, the level may drop—top up to the COLD FILL line as needed. Do not let the tank run dry.
5. Heat‑soak and recheck: After fans cycle and both heater hoses are hot, shut down and allow to cool completely. Recheck and adjust level. The diesel may require 1–2 additional heat cycles to fully purge micro‑bubbles.
6. Final checks: Inspect for leaks, confirm reservoir level at the COLD FILL mark, and verify stable operating temperature on the next few drives.

Tips:

• Do not mix conventional green coolant with DEX‑COOL. If contamination is suspected, thoroughly flush before refilling with fresh DEX‑COOL.
• Use distilled or deionized water when mixing from concentrate.

Common cooling system issues (2020–2024 Silverado HD)

• Water pump seepage/noise: More common as mileage climbs; look for crusty orange residue at the pump weep hole and coolant smell after shutdown.
• Radiator end‑tank or seam leaks: Plastic‑aluminum radiators can develop hairline seepage; watch for damp spots near the side tanks.
• Heater hose quick‑connect leaks: The plastic quick‑connects at the firewall or near the water pump can drip under pressure/heat.
• Thermostat faults: Stuck‑open thermostats cause long warm‑up and low cabin heat; stuck‑closed leads to overheating under load.
• Reservoir cap failure: A weak cap can lower system pressure and allow boil‑over; replace if you see dried coolant around the surge tank neck.
• Duramax diesel specifics: The large system volume means small leaks can take time to show on the gauge; EGR‑cooler or hose seepage can present as gradual coolant loss without obvious puddles. Pressure‑test if the level slowly drops.
• Aftermarket or incorrect coolant: Using non‑OAT or mixing chemistries can form sludge/gel and restrict heater cores—flush thoroughly and refill with the correct DEX‑COOL.

If you need capacity confirmation for your exact VIN or configuration, consult the GM service information or parts counter with your VIN.

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