1993 GMC Safari Owner's Manual - Page 220

How to Add Coolant to the Radiator I PO422 I 1. You canremovetheradiatorpressurecapwhenthecoolingsystem, includingtheradiatorpressure capandupperradiatorhose,isnolonger hot. Turn thepressurecapslowlytotheleftuntil it firststops.(Don't pressdownwhileturningthepressurecap.) If youhear a hiss,waitforthat pressure left. to stop. A hissmeansthere is still some turn it. 2. Thenkeepturningthepressurecap,butnowpushdownasyou Removethepressurecap. r .&-:.' : , .,. . .A. E 3. Fill theradiatorwiththeproper 5-1 4 5 PO423 mix, up to thebase of thefiller neck.