Quote:
Originally Posted by Stevo
On one of the "later" engines I went back to the "diaphragm" type pumps found in the early W123. The top of the air cleaner had to be swapped out for one with a vacuum fitting. The rebuild kits for those pumps are considerably cheaper also. They can, of course, lose their ball bearings too 
One cause of a vacuum pump going south with catastrophic results is "for and aft (laterel?) play in the timing device due to a worn bushing on the intermediate shaft. If the timing device can be pushed back and forth more that 1mm, beware |
After reading this thread I went looking and found as you say the diaphragm pump is cheaper to rebuild but I could find no one that sold the rebuild parts for the arm and bearing.
I also found there are 12 volt electric vacuum pumps made to power the Power Brake Boosters on gassers that have special camshafts or Blowers/turbos on the engines. But, new one are in the $270-$300 range.