Replacing a clutch Master cylinder on an 85 528e

Having done that job many times, I feel your pain! To start with, the thing that wears out in the master cylinder is the piston and not the cylinder or body of the master if you follow my meaning. My method involves extracting the piston from the new master cylinder and installing it in the master in the car, an internal snap ring pliers set is needed. If this is not an option you feel comfortable with then go under the car and remove the line from it's anchor point(where it attaches to the flexible hose) That will allow you to get at the fitting. Reinstall and bleed system. If at first the pedal seems "mushy" rapidly pump the pedal with your hand 10-20 times, then repeat as needed. These systems will eventually self purge trapped air.