So the other day I was driving down the highway and noticed a loss of power, looked at the temp gauge, and my engine was hot. I pulled of the highway to let it cool down. The coolant level was a bit low, but I didn't want to add cool coolant to hot. I resumed driving after a few minutes and was going to add it after my class. I got out of class and went to add the coolant and lo and behold, my coolant level was back up. Does anyone know what would cause this?