Driving my 2007 gas Safari Simba 8.1 GM engine south on 287 in Wyoming today. Rolling hills,nothing major. Temperature in low 80's,I was towing my Jeep Sahara. As it warmed, I turned on the dash air. ...
The first thing I would consider is what's in it. Has it ever had the coolant changed? Has it had a thermostat? Is it dexcool? Doesn't really matter now but what type of coolant did you add?