Coolant Flush

This procedure drains, flushes, and refills the engine cooling system with fresh DEX-COOL coolant to maintain proper engine temperature regulation and prevent corrosion.

Warnings

Tools required

Parts

• Radiator drain petcock seal (if deteriorated) × 1 — Use OEM specification

Fluids

• ACDelco DEX-COOL (Orange) — 18 qt

Preparation

1. Ensure engine is completely cold to the touch (no operation for at least 2 hours)
2. Park vehicle on level surface and engage parking brake
3. Place wheel chocks behind rear tires
4. Gather drain pans and position one under the radiator drain area
5. Have at least 18 quarts of fresh ACDelco DEX-COOL coolant available

Procedure

1. 1

   Remove radiator cap
   Slowly rotate the radiator cap counterclockwise to the first stop and allow any residual pressure to release. Once pressure is relieved, press down and continue rotating to remove the cap completely. Inspect cap gasket for damage or deterioration.
2. 2

   Locate and access radiator drain petcock
   The radiator drain petcock is located on the lower driver side corner of the radiator. Access may require reaching from underneath the front of the vehicle. Position drain pan directly beneath the drain petcock to catch coolant.
3. 3

   Open drain petcock and drain coolant
   Turn the drain petcock counterclockwise to open. Allow all coolant to drain completely into the drain pan. This will take 10-15 minutes. Once flow stops, inspect the petcock seal for cracks or deterioration and replace if necessary.
   ⚠Coolant may drain rapidly initially. Ensure drain pan is properly positioned to prevent spills.
4. 4

   Drain engine block if equipped with drain plugs
   On the L83 engine, check both sides of the engine block near the freeze plugs for drain plugs (not all configurations have them). If present, remove drain plugs with appropriate socket and allow block coolant to drain. Inspect drain plug sealing washers and replace if damaged.
   ℹ️Some model years may not have engine block drain plugs. If not present, proceed to next step.
5. 5

   Close drain petcock
   Once draining is complete, rotate the drain petcock clockwise until hand tight. Do not overtighten as this can damage the plastic threads on the radiator tank.
   Torque spec

   Drain Petcock7 Nm (5 lb-ft)
6. 6

   Install engine block drain plugs
   If block drain plugs were removed in step 4, reinstall them with new sealing washers if available. Torque to specification.
   Torque spec

   Block Drain Plug25 Nm (18 lb-ft)
7. 7

   Flush cooling system (optional but recommended)
   Close drain petcock and fill radiator with distilled water. Install radiator cap, start engine, and allow to reach operating temperature with heater on full hot. Shut off engine, allow to cool completely (2+ hours), then drain water. Repeat until drained water runs clear. This removes old coolant residue and contaminants.
   ⚠️Do not remove radiator cap when engine is hot or running. Allow complete cooling between flush cycles.
8. 8

   Locate and open bleed screw
   The cooling system bleed screw is located on the thermostat housing on the driver side of the engine. Use appropriate socket to loosen the bleed screw 2-3 turns. Leave it open during the filling process to allow air to escape.
9. 9

   Fill cooling system with DEX-COOL
   Using a funnel, slowly pour pre-mixed 50/50 DEX-COOL coolant into the radiator fill neck. Pour slowly to minimize air entrapment. Continue filling until coolant begins to seep from the open bleed screw, indicating air has been purged from that portion of the system.
   ℹ️Use only ACDelco DEX-COOL orange coolant. If using concentrated coolant, mix 50/50 with distilled water before adding.
10. 10

    Close bleed screw
    Once coolant flows steadily from the bleed screw without air bubbles, close the bleed screw by torquing to specification. Wipe away any spilled coolant.
    Torque spec

    Bleed Screw7 Nm (5 lb-ft)
11. 11

    Complete radiator fill
    Continue adding coolant to the radiator until the level reaches the base of the radiator neck. Install the radiator cap hand tight. Check the coolant overflow reservoir and fill to the COLD FILL line with DEX-COOL.
    Torque spec

    Radiator Cap1 Nm (1 lb-ft)
12. 12

    Burp cooling system
    Start the engine and allow it to idle with the heater set to maximum heat and fan on high. Monitor temperature gauge to ensure it remains in normal range. Run engine until the cooling fans cycle on and off at least twice (approximately 15-20 minutes). This confirms the thermostat has opened and coolant is circulating fully.
    ⚠Monitor temperature gauge continuously. If gauge approaches the hot zone, shut off engine immediately and investigate for air pockets or other issues.
13. 13

    Final fill and inspection
    After engine has fully warmed and fans have cycled, shut off engine and allow to cool for 30 minutes. Carefully remove radiator cap (system will still have some pressure) and top off radiator to the fill neck as needed. Also top off overflow reservoir to COLD FILL line. Reinstall radiator cap. Inspect all drain points and connections for leaks.

Reassembly

1. Wipe down any coolant residue from engine bay and radiator area with shop towels
2. Dispose of used coolant properly at a recycling facility or auto parts store that accepts coolant
3. Record the coolant service date and mileage for maintenance tracking

Verification

• Start engine and verify temperature gauge operates normally and reaches operating temperature within 5-10 minutes
• Confirm both upper and lower radiator hoses become hot, indicating proper coolant circulation
• Verify cooling fans activate when engine reaches operating temperature
• Check heater output blows hot air at idle and while driving
• Inspect radiator, hoses, drain petcock, and bleed screw for any coolant leaks
• After 24-48 hours of driving, recheck coolant level in overflow reservoir and top off if needed (some air purging is normal)
• Monitor coolant level weekly for the first month to ensure no ongoing leaks or air pocket issues

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