Bleeding the Clutch System
Here's what I've learned about bleeding clutches (specifically E34 but probably applies to others). First, almost unanimous that it can be a major pain
There are 2 problems: 1) the clutch slave bleeder points down so fluid can drain from the slave when you open the bleeder and air can pocket above it in the slave; 2) the blue braided fabric hose from the brake/clutch reservoir to the clutch master is too long/not enough drop which lets air trap in it.
My ordeal started by changing brake fluid and wanting then to get the old fluid out of the clutch system. So we bled the clutch but lost pedal (reason 1)) as we did (assistant communicated this too late in the game). Previously, we have done this succesfully. Onward, looked up in Chilton and it says to remove slave and orient nipple up, and bleed by pushing slave piston by hand. Did this - didn't work. Reason is that by now air was trapped in the feed tube to the clutch master.
Solution to the too long clutch master feed hose is to manually contort it to work the air out. First pull it front & up to get air from the master and then push where your holding down so that the air goes into the reservoir. IT GURGLED - there was that much air in it! Also recommended was tapping the hose to get the air out and, the more permanent fix, shortening the hose - I haven't done it - YMMV.
We tried bleeding the slave then in normal fashion (pump 10 times, hold, bleed, in situ). Didn't work - see reason 1) above but it seemed to get the air out of the master and lines. Therefore removed slave (2 13 mm nuts, use 6" extension) and bled air by manually pushing the slave piston. Could also try vacuum/pressure(preferred) bleeding at this point and/or opening the bleeder and single push strokes on the clutch pedal. (I didn't have a pressure bleeder but I'm guessing a caution is to not use a lot of pressure since the slave isn't pushing on anything.)
Thanks much to the bmw-digester's who responded via e-mail and to CCA ombudsman Scott Chamberlain (and Gene - last name withheld). Several responded with a cute trick to inject fluid into the slave and thereby charge the entire system, slave, master & hoses, from below. I am told, you can inject using an oil squirt can, vet syringes, or the pressurized fluid from a brake caliper bleeder nipple. While a nice trick, I worry about dirt/water/air contamination of the fluid and air leaking by the bleeder threads - perhaps these are not a problem so I pass it along.