Marshall pointed out <<< The latest ones have four screws on the outside and are supposed to be somewhat longer lived than the earlier ones with the front cover that's crimped on, but from what I've heard, they are starting to fail at about 200kmi. I expect the life of the pump is very closely related to how clean the oil remains! >>>
The disheartening news - my recently failed vacuum pump is a Peirburg with the four screws that hold on the cover. It failed at only 143k miles. Of course, I didn't get the PO's oil change records for the first 102k miles. I can only tell you that for the last 42k miles (mostly highway) it has used Mobil 1 changed at 5k mile intervals. I replaced the crimped on cover vacuum pump of my other 124 at ~ 320k miles and it was still functioning fine. I replaced that one because I learned from this list about the problems caused when these pumps fail. My current recommendation is for anybody that buys a 124 with ANY number of miles on it, replace the vacuum pump immediately. Then perhaps consider future replacements at 200k mile intervals. Ned Kleinhenz '95 E300D x2 '85 300D '80 300TD
