1996 Chevrolet Astro Owner's Manual - Page 186

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. 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. 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 NEUTRAL (N); otherwise, shift to the highest gear while driving - AUTOMATIC OVERDRIVE (a) or DRIVE (D). If you no longer have the overheat warning, you can drive. Just to be safe, drive slowerfor 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 @'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.