Cooling system - bleed: http://www.bmwtechinfo.com/repair/main/561en/htm/334.htm Here's the entire E30 factory shop manual, for your other projects! http://www.bmwtechinfo.com/repair/main/561en/htm/002.htm
There is a bleeder screw at the top of the thermostat housing. Start motor and bring up to temp, then slowly open bleeder until nothing but coolant comes out, in other words no more air. Buy the Bentley repair manual for the E30. It will pay for it's self in one use. Even though the ix is not in the manual there is enough related stuff to make it worth it. For instance your question here.
