GMC 1996 Sierra Owner's Manual page 227

If No Steam Is Coming From Your Engine
If you get the overheat warning but see or hear no
steam, the problem may not be too serious. Sometimes
the engine can get a little too hot when you:
Climb a long hill on a hot day.
0
Stop after high-speed driving.
Idle for long periods in traffic.
Tow a trailer. See "Driving on Grades" in the Index.
If you get the overheat warning with no sign of steam,
try this for a minute or so:
I . I f you have an air conditioner, turn it off.
2. Turn on your heater
to full hot at the highest fan
speed and open the window as necessary.
3 . If you're in a traffic jam, shift
to
NEUTRAL (N);
otherwise, shift
to the
highest gear while
driving
--
AUTOMATIC OVERDRIVE
(0)
o r
THIRD (3) for automatic transmissions.
If you no longer have the overheat warning, you can drive.
Just to be safe, drive slower for about 10 minutes. If the
warning doesn't come back on, you can drive normally.
If the warning continues, pull over, stop, and park your
vehicle right away.
If there's still no sign of steam, push the accelerator
until the engine speed is about twice as fast as normal
idle speed. Bring the engine speed back to normal idle
speed after two or three minutes. Now see if the warning
stops. But then, if you still have the warning, turn o f
the
engine
nrzd get
everyone
nut
o f the vehicle until it
cools down.
You may decide not to lift the hood but to get service
help right away.
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