I am having coolant problems as well. I have a 2006 525i with 85K miles. The coolant light started coming on and I was having to top the system weekly. Now it is daily and I was just adding water. I was just advised that water is a no no and I must use coolant. Unfortunately, I just lost my job and there is no cash to make expensive repairs.
Does anyone have any diagnostic tips? Back in the spring,l I had a dealer check it out and they could not locate the problem. However today after speaking with someone at an auto supply store, We looked under the hood and it does appear there are some fluids in the underbody of the vehicle.
Thanks for any assistance you can provide!