Recently the check engine coolant temp light has came on on my '01 silverado. The first time it happened I started my truck and the light came on immediately and the gage was maxed out. BUT after idling for about a minute, the temp came back down to normal operating temp. The second time the light came on happened about a week after the first time. This time I was on the highway doing 70 or so. The light came on and the gage was maxed but again it started to come back down slowly to normal. I pulled over and checked my radiator resevoir level and it was good. Can anyone help me out here? what should I do?