Cooling System: Service and Repair

CAUTION: Before draining and recovering the cooling system, inspect the system. Perform any service needed to ensure that the system is clean. Does not leak and is in proper working order. Some coolant manufacturers are mixing other types of glycol in their coolant formulations propylene glycol is the most common new ingredient, HOWEVER, PROPYLENE GLYCOL IS NOT RECOMMENDED FOR USE IN GM VEHICLES THAT WERE MANUFACTURED WITH GM GOODWRENCH DEX-COOL. A hydrometer will not always provide a correct measurement of freeze protection when anything other than ethylene glycol and water is being tested. The degree of inaccuracy will very depending on the proportion of other glycols present in the coolant. Hydrometers test the amount of glycol in a mixture by measuring the specific gravity of the mixture the more ethylene glycol the higher the float balls go, and the better the freeze protection. Because ethylene glycol and propylene glycol do not have the same specific gravities, hydrometer readings of mixtures containing propylene glycol give incorrect values. It is recommended that a refractometer be used when testing coolant. Refractometers test for the amount of glycol in a coolant mixture by measuring the speed of light as it passes through the fluid and are not affected by the specific gravity of the glycol. For proper coolant testing, refer to Testing Coolant Concentration in this section.

DRAINING
1. Park the vehicle on a level surface.
2. Remove the surge tank cap, when the engine is cool, by:
^ Slowly rotating cap counterclockwise about a 1/4 turn and then stop.
^ Wait until any residual pressure (indicated by a hissing sound) is relieved.
^ After all hissing stops, continue to rotate counterclockwise until the cap is removed.
3. Open the radiator drain valve located at the bottom of the radiator tank. For procedures requiring the cooling system to be partially drained, opening the radiator drain valve should provide sufficient draining; and no further actions should be necessary.
4. Remove engine block drain plug.
5. Allow the coolant to drain completely.

CAUTION: If the coolant is discolored, flush the cooling system. If the coolant appearance is normal, continue with the filling procedure.

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

REFILLING
1. Close the radiator drain cock and remove the drain hose.
2. Reinstall engine block drain plugs if previously removed.
^ Use pipe sealer GM PIN 12346004 when installing drain plugs.
3. Fill the surge tank to the base of the filler neck.

NOTE: Open the coolant air bleed valve on the top of the thermostat bypass pipe/heater pipe assembly. Once a continuous stream of coolant is expelled from the valve, close the valve.

4. With the pressure cap off, start the engine and let it run until the upper radiator hose starts to get hot.
5. If the coolant level in the surge tank is low, add the proper mix of coolant until the level reaches the full cold line.
6. Install the cap onto the tank with hand tight pressure.
^ After servicing the cooling system, an occasional intermittent low coolant light (if equipped) may be encountered during some extreme driving maneuvers. This complaint should be eliminated be removing the surge tank cap and adding coolant to a level just at or above the full cold line when the system is cold.