Put the sealer, a small bead, in the rubber before the glass. Put the glass in the rubber then the chrome and then rope into the chassis.

Do not use urethane sealer it will not work! You want to use either MB sealer MB window sealing compound, Part number 001 989 31 20 made for these older cars or 3M glazing (can't find the number now will post later)

My car is a 116 as well.

Good Luck!

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1980 300SD Manganese Brown Metallic Clearcoat 248k
1979 300SD White 148 k
1984 300D Silver project car for daughter
1982 300D wrecked
1980 300SD 310K not running