GM Service Manual Online
For 1990-2009 cars only

The cooling system consists of the following major components:

    • Radiator
    • Coolant recovery reservoir
    • Cooling fans
    • Thermostat
    • Water pump
    • Engine coolant air bleed pipe
    • Engine coolant temperature (ECT) sensor
    • Transmission oil cooler
    • All related hoses
    • Fan shroud
    • Fan motor/blade

The cooling systems functions is to maintain an efficient engine operating temperature during all speeds and under all operating conditions. Cooling systems are designed to remove about one-third (30 to 35 percent) of the heat produced in the combustion chambers by the burning of the air-fuel mixture. The engine is very inefficient while cold. Therefore the cooling system includes a devise (thermostat) that prevents normal cooling action during engine warm-up. The thermostat allows the engine parts to reach their normal operating temperature more quickly. This shortens the inefficient cold-operating time. When the engine reaches its normal operating temperature, the cooling system begins to function. The cooling system removes excess heat when the engine is hot, and slowly or not at all when the engine is cold or warming up.

The coolant absorbs heat as it passes through the engine. Then the hot coolant flows through a radiator in which the heat in the coolant is passed on to the air that is flowing through the radiator. The cooled coolant then flows back through the engine. This circulation of the coolant continually removes heat from the engine. The coolant is kept in circulation by the water pump.

Water jackets are designed to keep the cylinder block and cylinder heads cool. The water jackets are open spaces between the outside wall of the cylinder and the inside of the cylinder block and head. The coolant can circulate freely around the engine hot spots. These hot spots include the following:

    • Valve guides
    • Valve seats
    • Upper parts of the cylinder walls

When the engine is running at the normal operating temperature, coolant flows into the block and through the water jackets surrounding the cylinders. Vapor is vented off through the engine coolant air bleed pipe. Then coolant is forced through the head gasket openings and into the cylinder head water jackets. In the heads, the coolant flows around the combustion chambers and valve seat, picking up additional heat. From the heads, the coolant flows through the upper hose into the radiator. There, the coolant temperature is lowered, and the coolant is drawn again into the engine by the water pump to provide passenger compartment heat and defrost. The coolant recovery reservoir provides a coolant fill point. The reservoir is translucent for coolant level viewing.