System Description
This vehicle has a pressure-type engine cooling system. A thermostat
controls the coolant circulation.
A 103 kPa (15 psi) pressure-type radiator cap seals the
cooling system, causing the system to operate at a higher than atmospheric
pressure. The high pressure operation raises the boiling point of the
coolant to about 125°C (257°F) at sea level, increasing the
cooling efficiency of the radiator.
The pressure-vacuum valve radiator cap allows the coolant to expand
through the pressure valve in the center of the cap without building up unnecessary
pressure. The expanding coolant flows into the coolant recovery reservoir
and the vent valve closes because of coolant expansion and flow. The
nominal 103 kPa (15 psi) pressure will not be reached until
the system works at maximum capacity. Any air in the cooling system will
be forced into the coolant reservoir and out the vent tube at the top
of the reservoir. As the system cools, the coolant in the reservoir draws
back in the radiator through the vent valve, keeping the radiator full
at all times.
Engine Coolant Description
This vehicle was manufactured with GM Goodwrench DEX-COOL®. GM Goodwrench
DEX-COOL® was developed to last for 240 000 km (150,000 mi)
or 5 years, whichever occurs first. Make sure only GM Goodwrench DEX-COOL®
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: Do not use a solution stronger than 70 percent antifreeze. Pure antifreeze
can freeze at -22°C (-8°F).
|
| • | Give freezing protection down to -37°C (-34°F). |
| • | Give boiling protection up to 129°C (260°F). |
| • | Protect against rust and corrosion. |
| • | Help keep the proper engine temperature. |
| • | Allow the warning lights and gauges to work correctly. |
Uncommon Cooling System Problems
Problems not requiring disassembly of the cooling system:
| • | Large obstructions that block the radiator or the air conditioning
condenser can reduce the cooling efficiency of the cooling system. The following
are some examples of large obstructions: |
| • | The engine oil is overfilled. |
| • | An incorrect radiator for the application. Check the part number. |
| • | A loose, damaged or missing air seals. |
| • | A missing or damaged lower air baffle/air deflector. |
| • | An incorrect ignition timing. |
Problems requiring disassembly of the cooling system:
| • | An incorrect or damaged fan |
| • | Faulty emission system components (could cause overheating at
idle) |
| - | Positive Crankcase Ventilation (PCV) valve |
| - | Damaged thermal vacuum valve (TVV) |
| - | Damaged engine coolant temperature sensor (ECT) |
| • | Pressure testing the cooling system with the radiator cap installed
(shows if the pressure cap leaks because of radiator filler neck damage. |
| • | Worn or damaged water pump |
| - | Impeller vanes eroded or broken |
| - | Worn or damaged bearing or seal (Inspect for shaft or bearing
play.) |
| • | Plugged or incorrect radiator tubes (Perform a flow check.) |
| - | The cylinder head gasket |
| - | A damaged intake manifold or intake manifold gasket |
| • | Plugged coolant passages in the cylinder head(s) (Perform a visual
inspection.) |
