Decided to replace with newer version of vacuum pump ... installation was quite simple and took about 1.5 hours ... did not take off the fan clutch. Was able to slip the old one out and new one in without much trouble.
I prised off the factory cover which is held on by bent over tabs and there was oil in the outer chamber that was leaking out through the bottom of the chamber.
Make sure you have a new gasket ... my new pump came without a gasket (I did not note this until too late on Saturday to get one ... I assumed it was there) and due to the need for the car the next day, I had to use the old gasket (with lots of sealant). Seems OK so far.
It seems to idle better following start ... I may be imagining this ... is there a relationship through the fuel control system?
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg