GMC 1997 Safari Owner's Manual page 232

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.
0 '
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:
1. Turn off your air conditioner.
2. Turn on your heater to full hot at the highest fan
3. If you're in a traffic jam, shift to NEUTRAL (N);
speed and open the window as necessary.
otherwise, shift to the highest gear while
driving -- DRIVE (D).
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
qff
the
engine and get everyone out
o f
the vehicle until it
cools down.
You may decide not to lift the hood but to get service
help right away.