Last year I performed the 60,000 mile tune-up on my E36 M3 myself. I replaced the air filter, the fuel filter, the sparks plugs and I cleaned the mass air filter. There was one replacement I didn’t do at the time, partly because I knew it would be a real pain in the butt.
That was to replace the cabin microfilter, the filter air travels through from the outside into the car. I knew the filter had been replaced a few years ago, so I put it off. This weekend I tackled the job, and it was every bit as inconvenient as I had feared.
On most BMWs replacing the microfilter is an easy process. On my E39 M5, you simply pop the hood, open the plastic reservoir at the top of the engine bay and replace the filter (actually two filters in the case of the M5). For some reason, in the E36 model BMW buried the cabin microfilter deep inside the dashboard, requiring the removal of multiple items to change the filter.
Complicating my research into how best to make this replacement were differing opinions from respected sources of BMW information. My E36 Bentley manual, usually the ultimate authority on all BMW matters, stated that the glove compartment/box had to be removed. Bavarian Autosport’s blog said that wasn’t necessary, and made the procedure sound as simple as removing a few screws and pulling out the old filter. Doug Vetter’s DIY site agreed with Bentley that removal of the glove box wasn’t necessary, but documented a number of components that needed to be moved to provide room to change the filter.
I decided to make a game time decision on the glove box. If I didn’t need to remove it, I wouldn’t. But when I removed the lower panel, I couldn’t see enough to figure out what to do next.
So I removed the glove box, and here the Bentley manual unexpectedly failed me. It showed removal six screws would enable me to pull the glove box out of the car. But there is a 10mm bolt directly above the glove box light, luckily shown by the instructions that came with the new microfilter. If it wasn’t for that, I might still be pulling on the glove box after removing the six screws, wondering why it won’t come free.
Once the glove box was out of the car, the cabin microfilter was still blocked by the air duct and an electrical harness. The air duct is held into place with a single plastic rivet, which amazingly I was able to pop loose without breaking. I was very careful putting pressure on the harness, since the last thing I wanted to do was damage some kind of electronics with too much force. Eventually by pushing upwards I was able to dislodge it.
Finally I had access to a knob that released the cover over the filter. At that point, it was easy to pull the old filter out, and slide the new one in.
Then I reversed everything. I still couldn’t see the slot the filter goes into, so reseating the cover was done by feel. Then I repositioned the air duct, popping the rivet back in to keep it in place. While I was doing this replacement I noticed my alarm/keyless entry module seemed to be just sitting on top of the duct — I hit it with some duct tape to keep it still.
There is no reason that such a basic replacement should be so complicated and time consuming. But since it is, I hope this story and these images help the next owner tackling this as a DIY project.
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