1997 GMC Suburban Owner's Manual - Page 257

I Steam and scalding liquids fromhot cooling a system can blow out and burn you badly. They are under pressure, and you turn the radiator if pressure cap even a little they can come out at high speed. Never turn the cap when the cooling system, including the radiator pressure cap, is hot. Wait for the cooling system and radiator pressure cap to if you ever have to cool turn the pressure cap. -- -- 5-17