GMC 1994 Yukon Owner's Manual page 216

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.
Stop after high speed driving.
Idle for long periods in traffic.
Tow a trailer.
If you get the overheat warning with no sign of steam, try this for a minute
or so:
I . If 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
"N"
(Neutral).
If you no longer have the overheat warning, you can drive. Just to be safe,
drive slower for about ten 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 OFF THE ENGINE AND
GET EVERYONE OUT OF THE VEHICLE until it cools down.
You may decide not to lift the hood but to get service help right away.
Cooling System -Gas Engines
When you decide it's
safe to lift the hood,
here's what you'll see:
A. Coolant recovery
tank
B. Engine fm(s)
C. Radiator pressure
cap
5-12