it's most likely your steering rack thats leaking, and the reason why it isnt dripping on the ground is that all the fluid is going into one or both of the boots over the steering rack and tie rods and filling up like a water balloon. you will need to replace your entire steering rack. you can buy seal kits or rebuild kits, but they are not a easy job and you most likely wish you just paid a few hundred for a new steering rack. you can buy rebuilt factory steering racks from Ireland Engineering (
www.bmw2002.com ) for around $280 and from meridian auto parts
http://www.meridianautoparts.com/