Just the other day I was waiting for a train and waiting for my blazer to warm up. The tempature outside was 14 degrees. When I turned the heat on it was blowing cold air. I looked at the temp guage and it was climbing past 210 almost to 260. So I turned around and when I started to move again it came down slowly. I thought this was strange??? :shakehead The next day I was on the express way going about 60 mph Again being only 14 - 15 degrees outside the heat stopped and the temp shot up to 260. The check guages light came on. I slowed down playing with the heater changing from floor to vent to defrost and with in 2 to 3 minutes went back down to just below 210 where it normaly runs. My motor has 136000 miles on it, anybody have any idea? :banghead: . The blazer seems to run above 210 when it's 80 degrees outside on the highway. I've always been concerned with the temp guage and my eye is on it more than the fuel. I have no idea what could be wrong?

Bad Themostat.

One thread is enough.