1999 GMC Sonoma Owner's Manual - Page 213

yellowblue Engine Overheating You will find a coolant temperature gage on your vehicle's instrument panel. See "Gages" in the Index. CAUTION: Steam from an overheated engine can burn you badly, even if you just open the hood. Stay away from the engine if you see or hear steam coming from it. Just turn it off and get everyone away from the vehicle until it cools down. Wait until there is no sign of steam or coolant before you open the hood. If you keep driving when your engine is overheated, the liquids in it can catch fire. You or others could be badly burned. Stop your engine if it overheats, and get out of the vehicle until the engine is cool. If Steam Is Coming From Your Engine 5-9