The other day my 99 envoy w/4.3 temp started to rise from the usual temp of
190. I added some coolant because it was low. Now a week later the temp shot up almost to just under 260. I stopped and checked the coolant again and it was full. I loosened the radiator cap a little and some coolant came out so I know the radaitor is full. Now it runs at about 220 or so with a steady needle.Could the computer be telling it to run warmer for some reason?
There is 100,000 miles on it and it has every option if that helps.
Dave