1993 GMC Safari Owner's Manual - Page 267

Radiator Pressure Cap PO407 Your radiatorpressurecap is a 15 psi (105 kPa)pressure-type m n ._ must be tightly installed to prevent coolant loss and possible eng ...damagefromoverheating.Besure the arrowsonthepressurecap h e UD with overflow tube on the radiator filler neck. Whenyoureplaceyourradiatorpressurecap,an AC@ cap is recommended. Thermostat Enginecoolanttemperature is controlled by athermostatintheenginecoolant system.Thethermostat stops theflow of coolant through the radiator until the coolantreachesapresettemperature. Whenyoureplaceyourthermostat,an AC@ thermostatisrecommended. 6-29