2024 Chevrolet Silverado 2500HD — Coolant Capacity & Type

The 2024 Chevrolet Silverado 2500HD holds about 4.5–5.5 gallons (18–22 quarts) of coolant with the 6.6L gas V8, or roughly 6.5–8.0 gallons (26–32 quarts) with the 6.6L Duramax diesel, depending on configuration and how thoroughly it’s drained.

Quick answer

• Total cooling system capacity:
  • 6.6L V8 gas (L8T): about 18–22 qt (17.0–20.8 L)
  • 6.6L Duramax diesel (L5P): about 26–32 qt (24.6–30.3 L)
• OEM coolant spec: GM Dex-Cool, orange, OAT (Organic Acid Technology). Use coolant labeled “DEX-COOL Approved” (ACDelco Dex-Cool is the OE fill). Do not mix with conventional green or hybrid coolants.
• Mix ratio: 50/50 coolant and distilled water (or ready-mix 50/50). In very cold climates, up to 60/40 (coolant/water) is acceptable; never exceed 70% coolant.

Capacity by engine option

If you’re topping up only, add to the “COLD FILL” line on the surge tank—don’t overfill.

Flush interval

• Normal service: Replace Dex-Cool at 150,000 miles (240,000 km) or 5 years, whichever comes first. Subsequent changes typically follow the same interval.
• Severe duty (frequent towing/hauling, high-heat environments, dusty/off-road, extended idling): Inspect coolant condition yearly; many shops shorten to about 100,000 miles (160,000 km) or 5 years if tests show depletion or contamination.

Always service earlier if any component is replaced, if the system was contaminated with non–Dex-Cool, or if testing shows low freeze protection or pH out of spec.

How to refill & bleed

• Tools/supplies: Dex-Cool–approved OAT coolant (ACDelco recommended), distilled water (if using concentrate), drain pan, hose pinch-off pliers (optional), vacuum fill tool preferred, safety gear.
• Notes for this truck:
  • Both engines use a surge/degassing tank as the fill point. Many GM HD applications are self-bleeding through the surge tank; there is typically no separate manual bleeder. The Duramax’s complex cooling circuit makes a vacuum fill strongly advisable to prevent trapped air.

Step-by-step

1. Cool engine completely. Open the surge tank cap to relieve residual pressure.
2. Drain: Open radiator drain (lower tank, driver side) and disconnect the lowest hose if a more complete drain is needed. Capture and recycle coolant properly.
3. Close drains. If using concentrate, pre-mix 50/50 with distilled water.
4. Vacuum-fill (best practice): Pull vacuum on the system and ingest premix until the surge tank reaches the “COLD FILL” line.
   • If gravity-filling: Slowly fill via surge tank to the “COLD FILL” line. Pause and squeeze the upper radiator hose several times to burp large bubbles.
5. Heater on full hot, fan low. Start engine and idle. Watch for the thermostat(s) to open and for the upper hose to get hot.
6. Maintain level at the “COLD FILL” mark during warm-up; add as needed. Avoid overfilling—level will rise when hot.
7. Once at full operating temperature and the cabin heat is hot and steady, hold ~1,500 rpm for 2–3 minutes, then return to idle. Check for stable heat and no bubbling in the surge tank.
8. Shut down. Let the truck cool completely. Top off the surge tank back to the “COLD FILL” line.
9. Recheck over the next few drive cycles; small top-offs after purge are normal.

Common cooling system issues (2020–2024 Silverado HD)

• Surge tank cap or level sensor: Weak caps can vent early; level sensors may trigger false warnings if contaminated. Replace caps that don’t hold pressure and clean/replace faulty sensors.
• Hose quick-connect leaks: Heater-core and turbo coolant line connectors (diesel) can seep; inspect O-rings and retaining clips.
• Water pump seepage (6.6L gas): Weeping from the pump vent hole can appear at higher mileage; look for dried orange residue.
• Radiator end-tank seams: Plastic/aluminum interface may weep under heavy towing heat cycles; check for pink/orange crust along the crimp seams.
• Thermostat or bypass valve concerns: Slow warm-up or fluctuating temps can indicate sticking thermostats (the Duramax uses multiple thermostats).
• EGR cooler or coolant line leaks (Duramax): Internal EGR cooler leaks can cause gradual coolant loss and white exhaust on cold start; pressure test if unexplained loss occurs.
• Mixed coolant contamination: Adding conventional green or universal silicated coolant to Dex-Cool can cause sludge/gel; flush thoroughly and refill with Dex-Cool only.

Use only Dex-Cool–approved OAT coolant, ensure the surge tank cap holds the correct pressure, and vacuum-fill the Duramax for best results.

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