Hi, everyone. I'm new to the forum. I bought a used 2006 92X 2.5l with 130,720 miles in November 2017. I've barely driven it because I don't trust it. The used car dealership I bought it from replaced the head gaskets. I've had issues with it almost overheating. I replaced the thermostat and the temperature has remained steady. Yesterday, I noticed that coolant overflow tank is almost empty. It's not overheating. Should I be concerned? Thanks!