should be a small vacuum hose to the cruise control if it is original, it may not be an original cruise control system, not many w115 240D's had cruise.

The transmission does use vacuum on this model.

The main vacuum line coming off the vacuum pump goes to the brake booster, and the line should have 2 vacuum ports on it. One port should go over and have a blue and black check valve and then a 3 way connector, one green line runs to the vacuum tank and the other goes to the ac system. The other nipple should run over and have another blue and black check valve and then a 3 way and it should go to the vacuum tank for the door locks, and the other line should go inside the drivers front door.

__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg