What about popping the reservoir off first to get access, or is there a reason to leave it on the do the removal? This is an imminent job for me on my 1999 CLK 208. Thank you for taking your time to do the demo'.
You're correct, this job is 1000% easier if you simply remove the resorvoir first. This then gives far better access to the bolts that hold the master cylinder in place.
I don't know why you're tightening up the brake lines, when you haven't yet added any brake fluid into the resorvoir, and bled the master cylinder. The two most important parts of replacing a mastering cylinder - that you completely missed from the video.
