To replace the Air Filter Box in E30 models, first you should loosen the hose clamp at the air flow meter and then detach the hose. To remove the air flow meter electrical connection on 318 and M3 models, you have to twist out the outer ring and pull it off, then undo the four clips that hold down the upper filter housing against the lower chamber, raising out of the engine compartment an assembly consisting of an upper housing. As regards 325s, one needs to press down on a clip in order to release an electrical connector for the airflow sensor; after this is done, two nuts fixing the retainer of the Air Filter Box onto the mounting bracket must be taken away and if necessary - wire tie clamping on the electric lead should also be removed before lifting up the Air Filter Box from the engine bay. After that take off the Air Filter Box housing from the engine bay, disengage four spring-loaded latches holding together its top and bottom halves, lift up the top half. This will allow you to remove your filter element; please make sure there is nothing else left in the lower part of the Air Filter Box except debris that collected in it during service; after that reverse all steps for installation purposes. On E36s equipped with four-cylinder engines, pay attention to positioning a new seal so that it sits properly in the groove provided inside the intake manifold cover's lower half; besides do not forget about unsnapping those clips which serve as fasteners for the upper part of the Air Filter Box cover against its base. For six-cylinder motors all you need is just releasing some catches located around the external perimeter of the entire assembly containing the filtration cassette plus casing itself attached thereto by means of several screws accessible from under the bonnet; once this has been accomplished carefully lift the cassette up towards the ceiling removing it off the cage completely followed by wiping down assemblies prior to reinstalling parts again but now arranging them exactly opposite to the way according to earlier mentioned instructions provided hereabove: Only such action will help avoid any mistakes resulting in car malfunctioning because all above mentioned operations were carried out in the wrong sequence.
