Sounds like at least the wiper shaft could use lube.

There are many posts on this site regarding that. Try using the search feature, above right and use the key words: wiper lube

Keep us posted,

Haasman

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'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)