Draining and Filling Cooling Systems

Draining and Filling Cooling System (LS4)

Draining Procedure

Tools Required
J 26568 Coolant and Battery Tester

Caution: To avoid being burned, do not remove the radiator cap or surge tank cap while the engine is hot. The cooling system will release scalding fluid and steam under pressure if radiator cap or surge tank cap is removed while the engine and radiator are still hot.

Important: Draining the cooling system with the pressure cap installed will syphon the coolant from the overflow tank.

1. Remove the coolant pressure cap.
2. Place a drain pan under the drain cock.
3. Open the radiator drain cock.
4. Drain the cooling system.
5. If a complete engine block drain is required LS4 engine, remove the drain plugs.
6. Inspect the coolant.
7. Follow the appropriate procedure based on the condition of the coolant.
^ Normal in appearance - Follow the filling procedure.
^ Discolored - Follow the flush procedure.

Filling Procedure

Notice: This procedure must be followed. Improper coolant level could result in a low or high coolant level condition, causing engine damage.

Notice: Refer to Fastener Notice in Service Precautions.

1. Close the radiator drain cock.
2. If the engine block was drained for the LS4 engine, install the drain plugs.

Important: Use a 50/50 mixture of DEX-COOL antifreeze and clean, drinkable water.

3. Slowly fill the cooling system with a 50/50 coolant mixture until the coolant level is visible and stable.
4. Install the coolant cap loosely (threaded on about one turn).
5. Turn the heater blower fan to high.
6. Start the engine and raise the engine speed to 2,200 RPM and hold it there for 60 seconds, then shut engine off.
7. Remove the coolant cap and fill at the fill neck until the coolant level is visible and stable.
8. Install the coolant cap, threaded fully on.
9. Fill the coolant recovery bottle to the indicator line.
10. Turn the heater blower fan off.
11. Start the engine and run it above 3000 RPM until it is hot enough to open the thermostat, this will allow the trapped air to be purged from the engine.
12. After the thermostat has opened, complete a series of 3, four-second-duration idle to four-second-duration 3000 RPM cycles.
13. Turn the engine off and allow it to cool down enough to safely remove the coolant cap.
14. Remove the coolant cap and fill at the fill neck until the coolant level is visible and stable.
15. Install the coolant cap, threaded fully on.
16. Fill the coolant recovery bottle to the indicator line.
17. Inspect the concentration of the engine coolant using the J 26568.
18. Rinse away any excess coolant from the engine and the engine compartment.