My 1985 500sel with 220k with its big upright winshield had the same problem but it turned out to be lots of chips and age had made the winsheild bad you probley dont have the problem but if you have high milage you might.

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1985 euro 500sel 220k
1981 300sd 278k sold
1989 chrysler
leabaron 130k
1990 320sl (hopefully)