The cooling system maintains engine temperature at an efficient level during all engine operating conditions. The thermostat remains closed until the engine reaches proper operating temperature. When the engine is cold, coolant does not circulate through the radiator in order to allow for faster engine warm-up. When the engine reaches normal operating temperature, the thermostat opens, and coolant circulates through the radiator in order to keep the engine from overheating.

The cooling system consists of the following components:

The water pump draws coolant from the radiator and the coolant circulates through cooling jackets in the engine block, the cylinder heads, and the throttle body and plenum. The coolant is then directed back to the radiator to be cooled.

The new reverse-flow cooling system draws coolant from the radiator by the water pump and passes the coolant through the thermostat on the inlet side of the pump.

The coolant is routed through the cylinder heads first. Vapor, if any, is vented off through the air bleed pipe and the coolant travels down through the bores and into the block. Once the coolant leaves the engine block, the coolant returns to the water pump, where the coolant travels through a cast internal passage to the radiator.

The system directs some coolant through hoses to the heater core in order to provide for heating and defrosting. A sealed recovery reservoir connects to the radiator surge tank in order to retrieve the coolant displaced by expansion. As the coolant cools and contracts, vacuum draws the coolant back into the radiator surge tank.

The radiator surge tank provides a coolant fill point and a central cooling system air bleed location. A sensor in the radiator surge tank determines the coolant level. When the coolant in the system falls below the recommended level, a warning lamp in the instrument panel illuminates.

This vehicle has a newly developed engine coolant. GM Goodwrench DEX-COOL™ was developed to last for 166 000 km (100,000 mi) or 5 years, whichever occurs first. Follow the instructions in Draining/Filling Cooling System. Make sure only GM Goodwrench DEX-COOL™ (orange-colored, silicate-free) is used when coolant is added or changed.

A 50/50 mixture of ethylene glycol (GM Goodwrench DEX-COOL™) and water will provide the following protection:

Notice: Pure coolant can be added to raise the boiling point of the coolant, but too much will affect the freezing point. Do not use a solution stronger than 70 percent, as the freeze level rises rapidly after this point. Pure coolant will freeze at -22°C (-8°F).

The coolant temperature sensor is a variable resistance device. The resistance of the gauge will determine the position of the coolant gauge. As the coolant temperature increases, the sensor resistance decreases allowing more current flow through the sensor. This causes a higher temperature reading.