difficult find

[645i]

I have a 2000 x5 with a 4.4 I have recently replaced the expansion tank, high pressure steering hose, pcv valve, intake gaskets, throttle body gaskets, oil return lines, valve cover gaskets,upper and lower control arms. I did all this work myself but I can not find this leak! I assumed it was a coolant leak because I have had to top off every 2 weeks for the past month, I checked the vally pan and nothing same with all the coolant lines nothing leaking, no coolant in the oil so head gasket is fine. The leak is on the right side of the vehical, it is dripping down on to the thrust arm and it is blue. any ideas would be helpful