heating problem on 1997 BMW Z3

I have a new thermostat in my BMW Z3 but it stays normal when i am driving on the highway. When i go into town the car heats up and then goes back to normal and then heats up again. What is my problem?

by in Stephens City, VA on March 27, 2009
2 answers
ANSWER by , March 27, 2009
I would make sure that your cooling fan(s) work correctly and that your radiator flows properly. Are you driving with the A/C on? I ask this because there is a dedicated electric cooling fan for the A/C system when ever it is used and it should come on as soon as the A/C is engaged. If this is not working correctly your car will run hot when it isn't on the highway.
ANSWER by , June 27, 2010
When they added new coolant you need to purge the system of air.You can google the procedure like on the Peligan Parts web site. I had the same problem when the previous owner change coolant and did not purge the system. I have a 4 cylinder some ther are a little different steps. Drove me crasy at first but not overheating now air in radiator gave cooling fan a false reading and would not come on.