1999 GMC Sierra 1500 Pickup Owner's Manual - Page 251

If your vehicle has the four-wheel-drive option and the transfer case is engaged,adollymustbeusedundertherearwheelswhentowingfromthe front. Engine Overheating You will find a coolant temperature gage on your vehicle instrument panel. youhaveadieselengine,youwillalso find a low coolantlightonyour instrument panel. If Steam Is Coming From Your Engine: If K2509 I CAUTION A Steamfromanoverheatedenginecanburnyoubadly,even ifyou if yousee or hear justopenthehood.Stayawayfromtheengine it off andgeteveryoneawayfrom steamcomingfromit.Justturn thevehicleuntil it cools down.Waituntilthereisnosignofsteam or coolant before opening the hood. If youkeepdrivingwhenyourengine is overheated,theliquids cancatchfire. You or otherscould be badlyburned.Stopyour engine if it overheats,andgetoutofthevehicleuntiltheengineis cool. in it 5-9