1993 220 TE wiper lubrication

[cross]

I followed "Parrot of Doom's" excellent DIY article on lubricating the single wiper mechanism up to removal of the large plastic cover, however I was not able to expose the "piston" assembly as the make up of my wiper seems to be slightly different to that of the article.
The cover - the large plastic cover - seems to be a totally flush fit with no overlap . I removed the circlip around the piston from the top end of the large plastic cover but then ground to a halt as I could not figure out how the top came off - and not wishing to damage it irretrievably came to the forum.
Can anyone help please ?

 

[C220GJS]

Your wiper drive head is of an earlier design and the cover can only be removed once the complete drivehead/motor unit has been removed from the car as the securing screws are underneath the drivehead,see here;http://www.mercedesshop.com/shopforum/showthread.php?t=66429.
If you would rather not go to all that bother you can drill a small hole in the cover, insert the tube from a can of spray grease and spray liberally also lubricate the piston well where it exits the cover.