I am new to the group, I have an 88 chevy c1500 with a 305 in it. This morning I was on my way to work and out of the blue it over heated. Pulled over and after 10 minutes or so it cooled back down to normal. Went to work was fine, drove home it was fine. 2 hours after being home ran to town and overheated again. The radiator is hot. I live in michigan, thought maybe ice this morning but it should have iced again when I ran to town. Would this be a thermastat issue