Coolant: Service and Repair
DRAINING, FLUSHING AND FILLING THE COOLING SYSTEM
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 older types of glycol in their coolant formulations; propylene glycol is the most common new ingredient. 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 vary 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 "Coolant Concentration Testing" in this section.
Draining
CAUTION: To avoid the danger of being burned, do not remove the cap while the engine and radiator are still hot. Scalding fluid and steam can be blown out under pressure.
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. Insert piece of 5/16" fuel line tubing (or equivalent) through lower tie-bar and over the radiator drain.
4. Open the radiator drain valve located at the bottom left hand 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.
5. Remove engine block drain plug.
6. Allow the coolant to drain completely.
Important
^ Dispose of used coolant in a proper fashion, i.e., in a used coolant holding tank. NEVER POUR USED COOLANT DOWN The DRAIN!Ethylene glycol antifreeze is a very toxic chemical; disposing of it into the sewer system or ground water is both illegal and ecologically unsound!
Inspect
^ The drained coolant:
- If the coolant is discolored, flush the cooling system; refer to "Flushing" in this section.
- If the coolant appearance is normal, continue with the filling procedure; refer to "Filling" in this section.
Flushing
Various methods and equipment may be used to flush the system. If using special equipment such as a back flusher, follow the manufacturer's instructions. However, the thermostat should be removed before flushing the system.
Engine Coolant Recycling
As the need arises to conduct cooling system maintenance or repairs, all of the used coolant must be removed and replaced with qualified new or recycled coolant. If only the radiator is drained, up to 40% of the used, contaminated, coolant can remain in the cooling system. Used coolant removal (from the vehicle) can be accomplished by several methods:
^ Utilize waterless, coolant evacuation system available in the GM Dealer Equipment program (or equivalent) which removes the used coolant and replaces it with approved new or recycled coolant.
^ Utilize a GM approved coolant recycling system which recycles the coolant on the vehicle thereby eliminating the need for evacuation.
^ Recover coolant and store in a used coolant holding tank and submit the used coolant for recycling on a regular basis.
Filling
1. Close the radiator drain valve.
2. Install all engine block drain plugs if previously removed.
^ Use pipe sealer when installing drain plugs.
CAUTION: Under some conditions, the ethylene glycol in engine coolant is combustible. To help avoid being burned, DO NOT spill antifreeze or coolant on the exhaust system or hot engine parts.
3. Refill the cooling system with coolant meeting GM Specification 1825-M. To ensure sufficient engine cooling, freezing and corrosion protection, maintain the protection level at -37°C (-34°F) or lower. Use a solution that is no more than 70 percent antifreeze.
Important
When refilling the engine cooling system, add engine coolant supplement sealant, GM Part # 3634621 or equivalent, and coolant antifreeze meeting GM specification 1825-M.
- Add (2) crushed coolant pellets.
4. Fill surge tank with the proper mix of coolant to just above the "Small Cylinder" at the base of the tank opening or until the level reaches the "Split Line" formed by the black and tan parts of the tank.
5. With the pressure cap off, start the engine and let it run until the upper radiator hose starts to get hot.
CAUTION: Keep hands clear of fan.
6. If coolant is lower then "Small Cylinder", add proper mix of coolant to the surge tank until the level reaches the "Split line."
7. Install the surge tank pressure cap onto the surge 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 by removing the surge tank cap and adding coolant to a level just at or above the "Split Line" when the system is cold.