Caution: With a pressurized cooling system, the coolant temperature in the radiator can be considerably higher than the boiling point of the solution at atmospheric pressure. Removal of the surge tank cap, while the cooling system is hot and under high pressure, causes the solution to boil instantaneously with explosive force. This will cause the solution to spew out over the engine, the fenders, and the person removing the cap. Serious bodily injury may result.

Important: If you do not follow the procedure below, a low or high coolant level condition and/or vehicle damage could result.

1. Park the vehicle on a level surface.
2. Follow the steps below in order to remove the surge tank fill cap:

2.1.	Slowly rotate the cap counterclockwise.

2.2.	Stop rotating and allow the hissing to stop.

2.3.	After all hissing stops, continue turning counterclockwise in order to remove the cap.

3. Open the radiator drain cock.
4. Allow the system to drain completely.
5. Inspect the engine coolant for the following:

•	Discolored - follow the flush procedure below.

•	Normal in appearance - continue with the next step.

Notice: When adding coolant, use DEX-COOL® coolant. If silicated coolant is added to the system, premature engine, heater core or radiator corrosion may result. In addition, the engine coolant will require change sooner-at 50 000 km (30,000 mi) or 24 months.

•	The following notice applies only to the 4.8 L, 5.3 L, and 6.0 L engines.

Notice: DO NOT use cooling system seal tabs, or similar compounds, unless otherwise instructed. The use of cooling system seal tabs, or similar compounds, may restrict coolant flow through the passages of the cooling system or the engine components. Restricted coolant flow may cause engine overheating and/or damage to the cooling system or the engine components/assembly.

6. Close the radiator drain cock.
7. Fill the system through the surge tank opening.
8. Pre-mix a 50 to 60 percent solution of DEX-COOL® and clean, drinkable water.
9. Slowly add the pre-mixed solution to the surge tank until the level is slightly above the surge tank split line.
10. Start the engine.
11. Idle the engine for 1 minute.
12. Loosely install the surge tank cap. Do not allow the system to build up pressure.
13. Cycle the engine from idle to 3000 RPM in 30 second intervals until the engine coolant reaches 99°C (210°F) and the thermostat opens.
14. Shut off the engine.
15. Refer to step 3 in order to remove the surge tank cap.
16. Start the engine.
17. Idle the engine for 1 minute. Fill the surge tank to 1/2 inch above the COLD FULL mark on the surge tank.
18. Install the radiator surge tank cap.
19. Cycle the RPM. Idle the engine to 3000 in 30 second intervals until the engine coolant reaches 99°C (210°F).
20. Shut off the engine.
21. Top off the coolant, as necessary, to 1/2 inch above FULL COLD mark on the surge tank.
22. Rinse away any excess coolant from the engine and the compartment.
23. Inspect the concentration of the coolant.

1. Drain the cooling system, refer to the above procedure.
2. If equipped with the 4.3 L engine, remove the left and right engine block coolant drain plugs.



3. If equipped with the 4.8 L, 5.3 L, or 6.0 L engine, remove the left and right engine block coolant drain plugs.



4. If equipped with the 6.6 L diesel engine, remove the left and right engine block coolant drain plugs and washers.



5. If equipped with the 8.1 L engine, remove the left and right engine block coolant drain plugs.
6. Remove the engine block coolant heater, if equipped. Refer to Coolant Heater Replacement .
7. Allow the engine block to drain completely.
8. Apply sealant GM P/N 12346004 or equivalent to all drain plugs, EXCEPT the 6.6 L diesel engine plugs.
9. Re-install the engine block coolant drain plugs.

Tighten

•	Tighten the 4.3 L engine block coolant drain plug to 20 N·m (15 lb ft).

•	Tighten the 4.8 L, 5.3 L, or 6.0 L engine block coolant drain plug to 60 N·m (44 lb ft).

•	Tighten the 6.6 L diesel engine block coolant drain plug to 18 N·m (13 lb ft).

•	Tighten the 8.1 L engine block coolant drain plug to 60 N·m (44 lb ft).

10. Install the engine block coolant heater, if equipped. Refer to Coolant Heater Replacement .
11. Fill the cooling system, refer to the above procedure.