Step 1. Go buy yourself a Mityvac. Don't argue, just do it. Mine was a whopping $26 at AutoZone.

Then read this post on how the 240D vacuum system works.
http://www.peachparts.com/shopforum/showpost.php?p=428715&postcount=7

__________________
Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References