I didn't particularly want to find out that the PO had left water in my 280 SE, either! But I know what you mean! Oil collects there -- clean it all out and see how long it takes to collect again.
My Volvo uses a quart every 1000 miles or so, all of it ends up in the intake, but replacing valve guide seals on that engines is such a pain I've been putting it off. Probably need to, though, no need to waste oil.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!