where is the thermostat on 1990 olds custom crusier-single mom has to fix please. thanks

No the thermostat is not in the radiator u havr to follow the upper rad hose to the motor on the top and u will find the housing it sits in usually held in by 2 or 3 bolts and u will need a new gasket and make sure u clean both surfaces before u put it back together make the bolts tight but not too tight and run car with rad cap open and add antifreeze as it needs it hope that helps

thank you so much. wish us luck. going to give it a try in the am.