So I put the EBC pads in today. (
See this thread.) 32,000 miles and the rears were down to about 25%. (The fronts were replaced by the dealer a few months ago under warranty for a different reason.)
So I found it somewhat amusing that I had never really noticed the complete lack of a brake fluid reservoir anywhere in view in the engine compartment!. I looked in all the usual places under the hood - no reservoir! I looked in the manual. It says only "The brake fluid reservoir is located under the microfilter housing on the driver's side of the vehicle." I look again, under the filter - but in the engine compartment - no reservoir. I mean - I know what brake fluid reservoirs look like - has BMW changed the rules and put it in one of those big metal cannisters with a black lid? No. Couldn't be. now think. Really. Don't cheat.
Do you know where it is?
Well I do. Now, anyway. You really do have to
remove the air filter box (not just the filter itself) to access the reservoir!!!
Step 1:

Disconnect the outlet plumbing by lifting the 3 retaining clips. The plastic piece to which these clips are attached is actually a ring that floats around the tube. Knowing this will be helpful in reconnecting it later.
Step 2:
Disconnect the hood switch wire, and flip the metal bail up and over to the left to free the cover. Lift the front of the cover up, and then remove by sliding it forward. Note that the back of the cover has tabs which protrude through both the filter box and the plastic frame behind it. Knowing this will be helpful in repositioning the filter box later.
Step 3:
Squeeze the funny looking clip shown here, while pulling up on the front of the filter box. You do not need to remove the filter element first, but you did already because you were curious - no biggy. On my car the rubber seal around the front and inside edges of the box was actually glued to the rubber seal running fore and aft - however it comes away easily and will reseal when replaced without needing new glue. Note that the outboard, rear corner of the box has to come out from under and behind the frame. Knowing this will be helpful in repositioning the filter box later.
Ahhhh.
There's the sucker!