I have a 90 535i. I had overheating problem back in Sep. of 2000. I took the thermostat out and everything was good until this last two days. Late night I was driving around when the car started overheating. At first if went little over the middle line and went back. Then it went little over to the line before the red and it dropped back down. As I was pulling over it went to the red line. When I stopped it went back down to the middle. I don’t know what is wrong with it.