Joe,

I have not lifted the seat on my 300E, so I cannot say for sure, but on my 190E 2.3-16 the vacuum pump is an electrically powered unit, sits in a block of grey foam rubber, and has vacuum lines and power lines coming to it. It is on the passenger side of the car.

If this is missing you have a good explanation for why the system does not work. Check Fastlane as well as recycling places. Or E-Bay. Good luck, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)