let me till u that its impossible that ur trany leak water coz on the e36 they put its radiator external ( in front of the coolant radiator), so its not possible that the coolant water go to ur trany (if its auto), any way you have to follow all coolant lines one by one
fill up the coolant and check i know that the area is too narrow so if u couldn't found the leak you have unscrew the Intake Manifold that way u will be more able to see the water leak and here some useful web and pic's
http://www.pelicanparts.com/bmw/tech...e-Cleaning.htm
http://www.midnightautoworks.com/Ins...e/install.html
also if u let the temp of ur car at normal and switch it off maybe ur leak will increase so u can see where its ,