1995 GMC Yukon Owner's Manual - Page 320

NOTICE: Your surge tank pressure cap a unique 15 psi (105 kPa) is pressure-type cap foruse with surge tank cooling systems only. It mustbe tightly installed to prevent coolant and possible loss engine damage from overheating. sure the arrows on the cap Be line up with the top tube the coolant surge tank. of Thermostat Engine coolant temperature is controlled by a thermostat in the engine coolant system. The thermostat stops the flow of coolant through the radiator until the coolant reaches a preset temperature. When you replace your thermostat, an ACa thermostat is recommended. 6-38