Chevrolet EXPRESS - 2011 Manual page 297

If the overheat warning is displayed
with no sign of steam:
1. Turn the air off.
2. Turn the heater on to the highest
temperature and to the highest
fan speed. Open the windows as
necessary.
3. In heavy traffic, let the engine
idle in N (Neutral) while stopped.
If it is safe to do so, pull off
the road, shift to P (Park) or
N (Neutral) and let the
engine idle.
If the temperature overheat gauge
is no longer in the overheat zone or
an overheat warning no longer
displays, the vehicle can be driven.
Continue to drive the vehicle slowly
for about 10 minutes. Keep a safe
vehicle distance from the vehicle in
front. If the warning does not come
back on, continue to drive normally.
If the warning continues, pull over,
stop, and park the vehicle
right away.
If there is still no sign of steam,
push down the accelerator until the
engine speed is about twice as fast
as normal idle speed for at least
three minutes while you are parked.
If the warning is still on, turn off the
engine until it cools down.
If the decision is made not to lift the
hood, get service help right away.
The vehicle has a clutched engine
cooling fan. When the clutch is
engaged, the fan spins faster to
provide more air to cool the engine.
In most everyday driving conditions,
the fan is spinning slower and the
clutch is not fully engaged.
This improves fuel economy and
reduces fan noise. Under heavy
vehicle loading, trailer towing, and/
or high outside temperatures, the
fan speed increases as the clutch
more fully engages, so an increase
in fan noise may be heard. This is
normal and should not be mistaken
as the transmission slipping or
making extra shifts. It is merely the
cooling system functioning properly.
The fan will slow down when
additional cooling is not required
and the clutch partially disengages.
This fan noise may be heard when
starting the engine. It will go away
as the fan clutch partially
disengages.