For 1990-2009 cars

### General Description

The cooling system maintains an efficient engine temperature level during all engine operating conditions. When the engine is cold, the system cools slowly, or not at all, in order to allow the engine to warm up quickly.

The cooling system consists of the following components:

• | A radiator

• | A coolant recovery reservoir

• | Electric engine coolant fans

• | A thermostat

• | A coolant pump

• | An accessory drive belt

Cooling system operation requires the proper functioning of all components. The water pump draws coolant from the radiator and circulates the coolant through coolant jackets in the following areas:

• | The engine block

• | The intake manifold

• | The cylinder heads

The coolant is then directed back to the radiator where the coolant is cooled.

The system directs some coolant through hoses to the heater core to provide for heating and defrosting. A recovery reservoir connects to the radiator to recover coolant displaced by expansion from high temperatures, and to maintain the correct coolant level. As the coolant cools and contracts, vacuum draws the coolant back into the radiator.

### Long Life Coolant

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 this protection:

### Coolant Level Indicator Module

The coolant level indicator module activates a lamp in the instrument cluster when the coolant in the radiator goes below a certain level. The module is mounted on the right side tank of the radiator.

### Temperature Lamp Switch

This switch activates a warning lamp in the Driver Information Center (DIC) if the engine overheats. With optional instrumentation, a temperature gauge replaces the warning lamp and a transducer replaces the temperature switch. For location and diagnosis of the switch, refer to Temperature Lamp Switch in Electrical Diagnosis.

### Throttle Body Coolant System

The throttle body coolant system uses pipes and hoses to divert coolant to the throttle body. Coolant flows through the throttle body for cold weather starts and helps provide a smooth idle until the engine reaches operating temperature.

### Radiator Air Baffle Assemblies, Deflectors, and Seals

• | A deflector is designed to redirect air flow. Deflectors are installed under the vehicle and redirects the air flow beneath the vehicle to flow through the radiator.

• | The lower (1), side (3), and upper (2) air baffles are installed to direct air to the radiator and the A/C condenser.

• | Air seals are used to ensure that the air passes through the radiator and condenser, rather than bypassing them. A missing, damaged, or incorrectly installed baffle or seal may cause the engine to overheat.

### Cooling System Circulation

The coolant pump is belt-driven. Coolant from the radiator outlet flows to the coolant pump inlet and is then pumped through coolant passages in the cylinder block and then into the cavities that surround the cylinder liners. Coolant then flows through holes in the cylinder head gaskets into the cylinder head coolant passages and into the throttle body coolant system. Passages in the intake manifold direct the coolant to the thermostat at the rear of the manifold. When the thermostat is closed, the coolant is prevented from returning to the radiator and is recirculated for quick engine warm-up.

Once the engine sufficiently warms, the thermostat opens and coolant flows to the inlet tank on the top left side of the radiator. The coolant is cooled as the coolant flows across the horizontal core tubes to the outlet tanks on the right side of the radiator. This completes the coolant flow cycle.

### Coolant Temperature Fan Switch

• | This switch regulates voltage to the coolant fan relay, which operates the fan whenever the engine coolant temperature exceeds 110°C (230°F). For location and diagnosis, refer to Section 8A-31.

### Cylinder Block Plugs

• | For the location of the coolant jacket plugs in the cylinder block, refer to the Disassembled Views in the Engine Section. For removal and installation procedures, refer to Cylinder Block Plug Replacement in Engine Mechanical.