General Description
This vehicle has a pressure-type engine cooling system. A thermostat
controls the coolant circulation.
The cooling system consists of the following components:
| • | A radiator pressure cap (gasoline engines) |
| • | A coolant recovery reservoir (gasoline engines) |
| • | A coolant surge tank and surge tank cap (diesel engines) |
| • | A cooling fan and fan clutch |
| • | A coolant pump and pulley |
A 103 kPa (15 psi) radiator or surge tank 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), increasing
the cooling efficiency of the radiator.
The pressure-vacuum valve radiator cap, used with gasoline engines,
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. Any air in the system is forced into the coolant recovery
reservoir and then out of the vent tube at the top of the reservoir. As the
system cools, vacuum forces the coolant in the reservoir back to the radiator
through the vent valve. Because of this, the radiator remains full at all
times.
The diesel engine uses a cooling system with a surge tank. The pressure
cap for the diesel engine differs from the gasoline engine pressure cap. The
cap is on the surge tank. The diesel engine uses a pressurized surge tank.
Coolant circulates through the surge tank. The surge tank allows the escape
of any air in the system and provides room for coolant expansion when the
coolant is hot.
The cooling system reaches 103 kPa (15 psi) in either
system only after the system reaches normal operating temperature.
Engine 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 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).
| • | 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. |
| • | Let the warning lights and gauges 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; The following are some examples of large obstructions: |
| • | Front mounted bike carriers |
| • | Front mounte tire carriers |
| • | Missing or damaged air baffle or lower air deflector |
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 |
| • | Pressure testing the cooling system with the radiator cap installed |
| • | Plugged or incorrect radiator |
| • | The cylinder head gasket |
| • | A damaged intake manifold or intake manifold gasket |
| • | Plugged coolant passages in the cylinder head(s) |
| • | An incorrect thermostat that has been installed |
