1998 Chevrolet Blazer Owner's Manual - Page 249
1998 Chevrolet Blazer Manual
Page 249 highlights
JSteam and scalding liquids from a cooling hot system canblow out and burn badly. They you are under pressure, andyou turn the radiator if pressure cap even a little they cancome out at high speed. Never turn the cap when the cooling system, including the radiator pressure cooling system and cap, is hot. Wait for the radiator pressure cap to if you ever have to cool turn the pressure cap. IW to Add Coolant to the Radiator -- -- 1. You can remove the pressure cap when the cooling system, including the pressure and upper radiator cap hose, is no longer hot. Turn the pressure cap slowly counterclockwise until it first stops, (Don't press down while turning the pressurecap.) If you hear a hiss, waitfor that to stop. A hiss means there is still some pressure left. 5-17