I have developed a leak right at the top right corner of my rad ('97 328i). I dumped some rad stopleak in it and it was okay for a week or two and then the old "add coolant" message started flashing again. I could see where it had sprayed into the engine bay when the pressure got too high. I have nursed it along but the other day when i stopped the car my coolant began bubbling out from the filler cap all over my driveway. I haven't moved it since.
I am planning on replacing the rad myself and figure that this might be a good time to replace the water pump as well (I have about 65K miles on the car). I found this 'high performance' rad and pump combo at Bimmerworld Bimmerworld Shopping Cart
I would love it if anyone would like to coment on whether I am clueless or not when it comes to this particular situation.