BMW E30 Distributor Cap and Rotor Replacement

Distributor cap and rotor on BMW E30 are located at the front of the engine, and are easily identifiable as there are spark plug wires coming into (or from) it. Changing cap and rotor is an easy procedure on e30 and although removal of radiator and / or mechanical fan is not necessary, it would provide for easier access.
The distributor cap is protected by black plastic cover that can be removed by pressing on two tabs located at about half way on each cover side. Next remove three 8 mm bolts (bolt type and size might different between models), however note that they, once unfastened, do not separate from the cap. Set the distributor cap aside, and remove rotor by removing three 3 mm mounting screws (usually allen type). Pull off dust shield and inspect big O-ring. If it is crushed, or otherwise damaged, it should be replaced.

At this point you can remove sparkplug wire leads from the old distributor cap and connect them to the new one. When removing spark plug wires pull on the boot only and not on the wire itself. Actually, you could remove sparkplug wires as a very first step, however removing them now minimizes chances of a mistaken connection. Just unplug one wire from old cap and connect it to same location on the new one, and repeat for all wires. You can always check for correct installation since the ignition firing order is 1-5-3-6-2-4 and terminals on the distributor cap have a label. That means that spark plug wire from cylinder 1 goes to the terminal cap labeled 1 (cylinders are numbered sequentially with cylinder number 1 being closest to the front of the car).

Place back dust shield, then install rotor and tighten mounting screws to 3 Nm (27 in. lb.). Rotor can be installed in only one position so you don't have to worry about that, however make sure not to over-tighten the screws. Install distributor cap and tighten three associated bolts. Last step is to reinstall protective cover.