BMW: Z3 1998 Over Heating, impeller, water pump

Question
I have an overheating problem with Z3 1.9. I changed the radiator and the thermostat, still overheating. The fan is not coming on but works if I bypass it.  

Answer
Joe,
 Is the problem the fan?  If you bypass the fan, does the car still overheat?  If you have changed the T-stat, then the water pump is the only culprit left.  I know on some of the Z3's the impeller's were made of plastic, and they would crumble to pieces after a few years.  This would leave you with a water pump that doesn't pump water.  

 I would check this as my next step, and make sure to bleed the system correctly, or it will over heat again.

 Good luck,
 Josh