I was thinking of doing this. I got a Gallon of Dex Cool and some Water Wetter.

How hard is it to do it ????

What are the steps ?? Can someone guide me ?? I dont have a service manual.

 

Is it a LS! motor?....................With over 100K miles on it?......................

If so, drain and flush the entire cooling system then refill with Dexcool.

 

Here ya go

Draining and Filling Cooling System 5.7 L

Draining Procedure

Caution: As long as there is pressure in the cooling system, the temperature can be considerably higher than the boiling temperature of the solution in the radiator without causing the solution to boil. Removal of the pressure cap while the engine is hot and pressure is high will cause the solution to boil instantaneously -- possibly with explosive force -- spewing the solution over the engine, fenders and the person removing the cap.

NOTICE: When adding coolant, it is important that you use GM Goodwrench DEX-COOL® or HAVOLINE® DEX-COOL® coolant. If Coolant other than DEX-COOL® or HAVOLINE® DEX-COOL® is added to the system the engine coolant will require change sooner; at 50 000 km (30,000 mi) or 24 months.

1. Park the vehicle on a level surface.
2. Follow the steps below to remove the radiator pressure cap:
- Slowly rotate the cap counterclockwise until the cap reaches the stop. Do not press down while turning the radiator pressure cap.
- Wait until any remaining pressure, indicated by a hissing sound , is relieved.
- After all the pressure is relieved, press down on the cap and continue to rotate the pressure cap counterclockwise.
3. Open the radiator drain ****.
4. Remove the engine block coolant drain hole plugs.
5. Inspect the engine coolant:
- Discolored -- follow the flush procedure.
- Normal in appearance -- Continue with filling.
6. Allow the system to drain completely.
7. Close the radiator drain ****. Tighten the radiator drain **** to 2 N·m (18 lb in).
8. Install the coolant drain hole plugs. Tighten the drain hole plugs to 60 N·m (44 lb ft).

Flushing Procedure

1. Add enough water to fill the coolant system.
2. Run the engine until the thermostat opens.
3. Stop the engine. Repeat the draining procedure until the drained fluid is colorless.
4. Remove, clean, and reinstall the coolant recovery reservoir. (Refer to Coolant Recovery Reservoir Replacement.)

Filling Procedure

1. Complete the following steps in order to fill the coolant system:
- Fill the radiator to below the fill neck.
- Fill the coolant recovery reservoir to the FULL HOT mark.
- Install the coolant recovery reservoir cap.
2. With the radiator pressure cap removed, run the engine until normal operating temperature is reached. The radiator inlet hose will become hot.
3. With the engine idling, add coolant to the radiator until the coolant level reaches the bottom of the fill neck.
4. Install the pressure cap.
5. After the engine reaches normal operating temperature, check for coolant leaks.


Coolant Recovery Reservoir Replacement

Removal Procedure

1. Remove the battery.
2. Remove the coolant recovery reservoir hose from the radiator.
3. Remove the accelerator and cruise control servo cable bolts, if equipped with a 5.7 L engine.
4. Reposition the accelerator and cruise control servo cable adjuster, if equipped with a 5.7 L engine.
5. Remove the coolant recovery reservoir bolt.
6. Remove the wiring harness rosebud clip from the reservoir neck.
7. Remove the coolant recovery reservoir.
8. Remove the coolant recovery reservoir hose from the reservoir.
9. Clean the coolant recovery reservoir with soap and water. Thoroughly rinse the reservoir.

Installation Procedure

1. Install the coolant recovery reservoir hose to the reservoir.
2. Install the coolant recovery reservoir.
3. Install the wiring harness rosebud clip to the reservoir neck.
4. Install the coolant recovery reservoir bolt. Tighten the coolant recovery reservoir bolt to 12 N·m (106 lb in).
5. Position the accelerator and cruise control servo cable adjuster, if equipped with a 5.7 L engine.
6. Install the accelerator and cruise control servo cable bolts, if equipped with a 5.7 L engine. Tighten the accelerator and cruise control servo cable adjuster bolts to 8 N·m (71 lb in).
7. Install the coolant recovery reservoir hose to the radiator.
8. Install the battery.
9. Add engine coolant to the FULL COLD mark on the reservoir.


And while you're at it:

Radiator Cleaning

Caution: NEVER spray water on a hot radiator. The resulting steam could cause personal injury.

Important: Do not brush the radiator fins. The radiator fins are necessary for good heat transfer. Brushing damages the fins and reduces heat transfer.

Clean the front face of the radiator annually.
- Clean the front face of the condenser.
- Remove bugs, leaves, etc. by blowing compressed air through the radiator. Blow the air from the rear toward the front. If compressed air is not available, a water hose can be used to force water through the radiator. Use water only with the engine not running and cool.

 

One more hint! When refilling remove the line from the throttle body into the head on the drivers side. If you have the throttle body bypass it is much easier. Fill slowly untill coolant comes out of the head. Reattach the line and continue the above instructions. This helps get most of the air out of the system.