I couldn't locate orginal thread, but my roof antenna (GPS/Phone) cover broke off. I want to give the straight scoop. I'm a MB tech at a dealer. From Ebay I ordered a cover & seal kit from ebay seller AM-Autoparts. $24.95 free shipping. Do a Ebay search "Mercedes GPS antenna" & you'll see many sellers @ various prices. AutohausAZ also sells them. None are genuine MB so far as I can tell. (Genuine only supplied from dealer with plastic base, which is very costly & unneeded). It is most important you get the correct cover. DO NOT get the tapered cover as sold on ebay that is glued on with silicon or the like. It has part #2028270031. It is too fat & made for a hat shelf mouted type antenna. These wrong ones go for $5-15.
The correct replacment cover will be exactly like the original. Straight with 4 shallow grooves & a deep grove where it hooks into cover, with a small bell shape at bottom, & it also always comes with the base housing seal.
Here's what my experiance was: Part was made in Taiwan. Rubber seemed slightly different from genuine part, but no matter quality seemed fine.
You remove the antenna cover with a small allen wrench. Be mindfull not to loose the paper washer under the screw threads up inside the cover. It keeps water out. If the nut the screw goes into is loose or comes off with cover, reinstall it & thighten just snug. Check the nut in any case for loosness. Lift off the plastic base. May be quite stuck to roof. You will need to dig the fingernails under it to force up. Avoid prying with screw driver if possible! Lift off the cover. Pull out the remains of the old rubber cover. You will notice the hole is quite small compared to the cover. Don't push it in from the bottom. Take some liquid dish or hand soap & lube the hole & bottom "bell" of the cover. Squeeze the bell & force a bit of it in the hole. Keep pushing & working the edge of the bell in. Take your time, not so easy to do, but it will go. Verify the rubber cover is smoothly seated in the hole. Clean off soap & dry well.
Take a tiny bit of grease, oil, even a part drop from the dipstick... & put just a part drop in the screw threads to keep them from siezing in the nut. Put the base gasket on the plastic cover. Verify that paper washer seal is in place. Notice how thin the plastic recess is where the washer goes... Don't over tighten the cover or you will crush it! Now feed the antenna wire up into the rubber as you install the cover. Work it down easy & tighen the screw. You will see the gasket compress & the screw will start to feel tighter all of a sudden. That's it, just snug. Hardly even 2 fingers on the allen wrench handle.
Time will tell how well the replacement cover holds up, but for now, I saved well over $100.
Would be interesting to know if the more costly Ebay ones are different brand or quality. AutohausAZ sells ones made by URO a divsion (or product) of APA autoparts. My packaging had no maker name on it. Just part #1ABGS00056 PO#597243 Vendor:V0138 Anybody know what the maker is? By the way 210827002 is the MB # some sellers use for these. That is not a complete MB # for the part, & the dealer would be sent a complete assembly if you forced the # through MB parts.
Don

 

This is next on my to-do-list for my Wagen. Glad you took the time to share.

 

I have to replace the rubber stem on my W208 but your instructions are really comforting Thanks again for all the info you have provided

 

Need help..{2000 E430 Bose} the top part "black rubberized antenna," is missing. Also the only thing left of audio system is radio, which has weak signal reception. This car was equipped phone, CD and cassette player I believe with original equipment.
I just want a decent radio.

 

I used this as mine was the same way. Surprisingly it improved my reception. Very simple to install and inexpensive to get
http://www.ebay.com/itm/Roof-Antenna...dVX4H~&vxp=mtr