I think they are some sort of check valve, but I'm not sure exactly what they do...mine has them too. Maybe they regulate the amount of vacuum going to a particular component?...Just a guess.

If there's oil in your vacuum lines, you probably have a failing vacuum pump diagphram, better get it checked, it will eventually ruin your entire vacuum system...Oil eats the rubber vacuum lines!

Mike

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1979 300 SD
350,000 miles
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1982 300D-gone---sold to a buddy
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1985 300TD
270,000 miles
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1994 E320
not my favorite, but the wife wanted it

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