My '97 528i w/ 128K miles is presently doing the same thing. Its been doing it for 4 months. After a new water pump, thermostat, fan clutch, radiator, and exp tank, nothing is fixing it. What's magical is every time a mechanic fixes something, it's fine for a few weeks. But stop-n-go traffic, traffic lights, slow speed driving thru the mall parking lot, etc, is killing me. I can sit at a red light and watch the temp gauge go into the red. But, like you, revving it to 2000 rpm or more will get the gauge to come back down. And at hwy speeds overheating is never an issue, mainly since I have good airflow. Finally the mechanic OVER PRESSURIZED the cooling system and found a small leak in the head gasket. It hasn't been there long based on the amt of antifreeze scum that's built up. But every time a mechanic touchs the car, they top off the coolant. That's why it's fine for 2 weeks. But over time, as antifreeze steams out, the car is less water cooled and more air cooled, making things worse. It's sort of an exponential or snow-balling situation. You don't know it, see it, or smell it, but you are losing coolant when you drive. Both the dealer and an independent charge $2K+ to do the repair. I'm probably going to limp along and add coolant every morning while it's cold. If it gets worse I'll spend the $. But I hesistate since someone told me I could get my oil and coolant to mix, which is a far worse situation. The bottom line is, I've read numerous posts on here about over heating. This forum is great and has helped me tremendously. Everyone says check the obvious, but for me and $1.5K later, the obvious things were not the cause. Good luck, it's frustrating.