1998 Cadillac Catera Owner's Manual - Page 233

1. You can remove the coolant surge tank pressure cap when the cooling system, including coolant the surge tank pressure and upper radiator hose, is cap no longer hot. Turn the pressure cap slowly counterclockwise untilit first stops. (Don't press down while turning the pressure cap.) If you hear a hiss, wait for that to stop. hiss means A there is still some pressure left. 2. Then keep turning the pressurecap slowly, and remove it. 5-18