I thought this was covered earlier in the thread - maybe not. Most OM60x diesels up to about 1990 have the assembly basket left in from the factory. It must be removed if you use the 'dam' style gasket (see photo). The dam gasket is only required for engines prior to the engine #'s listed (for OM603 - I don't know about OM601/602 - may not apply to those). The basket retaining bolts hit the dam gasket, and it will deform and leak like a sieve (don't ask how I know). Later engines can leave the basket in place and use the 'outline' gasket. This is documented in the factory service manual - here's the relevant PDF file (scroll down a couple of pages):
http://www.meimann.com/docs/mercedes/OM603_vac_pump_mod.pdf
(1.4MB PDF file)
