Cooling system servicing (draining, flushing and refilling)

Warning: Do not allow antifreeze to come in contact with your skin or painted surfaces of the vehicle. Rinse off spills immediately with plenty of water. Antifreeze is highly toxic if ingested. Never leave antifreeze lying around in an open container or in puddles on the floor; children and pets are attracted by its sweet smell and may drink it. Check with local authorities on disposing of used antifreeze. Many communities have collection centers that will see that antifreeze is disposed of safely. Antifreeze is flammable under certain conditions — be sure to read the precautions on the container.

Caution: Never mix green-colored ethylene glycol antifreeze and orange-colored DEXCOOL silicate-free coolant because doing so will destroy the efficiency of the DEX-COOL coolant, which is designed to last for 100,000 miles or five years.


1. Periodically, the cooling system should be drained, flushed and refilled to replenish the antifreeze mixture and prevent formation of rust and corrosion, which can impair the performance of the cooling system and cause engine damage. When the cooling system is serviced, all hoses and the expansion tank cap should be checked and replaced if necessary.

2. Apply the parking brake and block the wheels.

Warning: If the vehicle has just been driven, wait several hours to allow the engine to cool down before beginning this procedure.

3. Move a drain pan under the lower right side of the radiator. Attach a length of hose to the drain fitting below the drain valve, direct it into the pan, then unscrew the drain valve (see illustration). Remove the expansion tank cap and allow the coolant to drain.

26.3 The radiator drain valve is located on the lower right corner of the radiator

Chevrolet Silverado  _ The radiator drain valve is located on the lower right corner of the radiator

1 Drain valve
2 Length of hose attached to the drain fitting

4. After coolant stops flowing out of the radiator and hose, move the container under the engine block drain plugs — there’s one on each side of the block (see illustration).

Note: On some models, a block heater is installed in place of a plug.

5. Remove the plugs and allow the coolant in the block to drain (see illustration).

26.5 Cylinder block drain plug — there is one on each side of the block (on some models it may be necessary to remove
the starter for access to the plug)

Chevrolet Silverado  _ Cylinder block drain plug - there is one on each side of the block (on some models it may be necessary to remove the starter for access to the plug)

6. While the coolant is draining, check the condition of the radiator hoses, heater hoses and clamps.

7. Replace any damaged clamps or hoses. Reinstall the drain plugs and tighten them securely, using Permatex 2. sealants on the threads of the plugs. Tighten the radiator drain valve.


8. Fill the cooling system with clean water, following the Refilling procedure (see Step 14).

9. Start the engine and allow it to reach normal operating temperature, then rev up the engine a few times.

10. Turn the engine off and allow it to cool completely, then drain the system as described earlier.

11. Repeat Steps 8 through 10 until the water being drained is free of contaminants.

12. In severe cases of contamination or clogging of the radiator, remove the radiator (see Cooling, heating and air conditioning systems) and have a radiator repair facility clean and repair it if necessary.

13. Many deposits can be removed by the chemical action of a cleaner available at auto parts stores. Follow the procedure outlined in the manufacturer’s instructions.

Note: When the coolant is regularly drained and the system refilled with the correct antifreeze/water mixture, there should be no need to use chemical cleaners or descales.


14. Tighten the radiator drain fitting.

15. Place the heater temperature control in the maximum heat position.

16. Slowly add new coolant (a 50/50 mixture of water and DEX-COOL antifreeze) to the radiator until the level is up to the bottom of the filler neck.

17. Install the radiator cap and run the engine at idle for two minutes, periodically raising the engine rpm to 2500 to 3000 rpm.

18. Turn the engine off and let it cool. Add more coolant mixture to bring the level up to the bottom of the radiator filler neck.

19. Repeat Steps 17 and 18 as necessary.

20. Start the engine, allow it to reach normal operating temperature and check for leaks. Also, set the heater and blower controls to the maximum setting and check to see that the heater output from the air ducts is warm. This is a good indication that all air has been purged from the cooling system.

21. Check the level of coolant in the coolant reservoir, adding as necessary (see Fluid level checks).

  • Pages

    open all | close all