The engine is kept cool by coolant circulating through the engine to a radiator where the heat to transferred to the air. The coolant is circulated by a pump driven by the engine accessory drive belt. The complete cooling system consists of a radiator, recovery system, cooling fans (electric on these vehicles) thermostat, pump and the serpentine drive belt.
All of the vehicles covered by this guide were originally filled at the factory with GM Goodwrench DEX-COOL®. DEX-COOL® is an ethylene-glycol coolant that was developed to last for 150,000 miles (240,000 km), or 5 years, whichever occurs first. It is recommended that only DEX-COOL® be used when coolant is added or changed. It's a good idea to purchase a gallon container or two of DEX-COOL® from an authorized GM dealer so the correct antifreeze is always available. A 50/50 mixture of this ethylene-glycol coolant and water should be used, providing freezing protection down to -34°F (1°C), boiling protection to 265°F (265°C), and rust and corrosion protection for the system. A solution stronger than 70% antifreeze is not recommended and pure antifreeze will freeze at only -8°F (-22°C).
A pressure vent radiator cap is used on all models to allow a buildup of 15 psi in the cooling system. This pressure raises the boiling point of coolant to approximately 262°F. at sea level. DO NOT remove the radiator cap to check the engine coolant level.
Always check the coolant level by looking through the "see through" area of the coolant recovery reservoir. Coolant should be added ONLY to the reservoir, after the system cools. Because a radiator cap, loosened when the engine is hot, will cause a loss of pressure and immediate coolant boiling, possibly with explosive force, most car makers, including GM, have designed the radiator cap in such a way that it is not easy to get a grip, to discourage inadvertent removal. Embossed on the cap is a caution against its being opened and arrows indicating the proper closed position. During routine maintenance, ALWAYS check the coolant level (and add, if required) at the coolant recovery reservoir. Refilling coolant at the radiator should only be required if the radiator and/or the cooling system has been drained.
DRAIN & REFILL
- With the engine cool, remove the radiator cap by slowly rotating the cap counter-clockwise to the detent (a stop that will prevent further turning). Do not press down while rotating the pressure cap. Wait until any residual pressure (indicated by a hissing sound) is relieved. After all hissing stops, continue to rotate counter-clockwise until the cap is removed.
- Place a drain pan under the vehicle to collect all of the drained coolant.
- 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 action should be necessary.
- Locate and open the air bleed vent(s). They are generally located on the thermostat housing. The air bleed vent should be opened two to three turns.
- Allow the coolant to completely drain from the radiator.
- Close the radiator drain valve.
Slowly fill the cooling system through the radiator neck using the following procedure:
- If the coolant system has been flushed (block drains opened), first add 100% DEX-COOL®. For the 3.1L engine, use 5.8 quarts; for the 3.8L engines, use 5.3 quarts; for the 3.4L engine, use 6.1 quarts.
- Then slowly add clean water to the system until the level of the coolant mixture has reached the base of the radiator neck.
- Wait for two minutes and recheck the level of the coolant mixture, and add clean water if necessary to restore the coolant mixture level to the base of the radiator neck.
- If the cooling system is being refilled ONLY (no flush), simply use a 50/50 mix of coolant and water to refill.
- Install the radiator cap making certain that the arrows line up with the overflow tube.
- Close the air bleed valve(s). DO NOT OVERTIGHTEN. The bleed valve is made of brass and easily damaged.
- Fill the coolant reservoir as required to bring the 50/50 mix to the COLD level mark on the reservoir.
- Start the engine and check for leaks.
FLUSH AND CLEANING
- Refer to the drain and fill procedure in this section, then drain the cooling system.
- Close the drain valve.
- If using a flushing solution, remove the thermostat. Reinstall the thermostat housing.
- Add sufficient water to fill the system.
- Start the engine and run for a few minutes. Shut the engine OFF . Drain the cooling system.
- With the engine OFF , and if using a flushing solution, disconnect the heater hose to the heater core, usually at the firewall. Connect a water hose to end of the heater hose and run water into the system until it begins to flow out of the top of the radiator.
- Allow the water to flow out of the radiator until it is clear.
- Reconnect the heater hose.
- Drain the cooling system again.
- Reinstall the thermostat.
- Empty the coolant reservoir or surge tank and flush it.
- Fill the cooling system using the correct ratio of antifreeze and water, to the bottom of the radiator filler neck. Fill the reservoir or surge tank to the FULL mark.
- Install the radiator cap, making sure the arrows align with the overflow tube.