First I have to say sorry for bringing up an old thread.....
I have had this problem three times on two of the Bimmers I own, my M5 (2000) and M3 (2004). Both have shown this natural rubber rot problem on the windshield. Now my M Roadster is showing this around the window seals.... so in reality its twice on the 5, once on the 3 and now the Roadster. GRRRR. I have used Gummi Fledge for the last two years, and it helps a lot, but in the end it does not prevent the eventual rot, even on new parts.
Now in fairness, I do live in a high heat area but I do park the cars in my garage so they don't bake in the sun.
Now to the point, replacment of the parts is not that hard nor is it that expensive (if you DIY), just time consuming for the DIYer and a general PIA to have to do it considering what these cars are and cost. It just shouldn't happen in my book. As someone else pointed out 'a POS 1968 car has better rubber!' That's disturbing that another car company makes better seal componet than BMW and it does not rot! Further, I'm disgusted that BMW won't take responsibility for it and repair it AT NO CHARGE to their costumer base, mostly because it IS a faulty material part in the first place. The slap in the face is dealing with BMW.... If you have them do it they charge four times the amount of what the job is worth, I've even had the local dealer tell me they would have to remove the windscreen. Anybody that has DIY on the E39 body knows that is a flat down fib. Don't get me going on the part mark up they charge! Better to buy it from a out source.
OK... I vented, off my soap box.... Has anyone ever had success with BMW, as pointed out in the earlier part of this thread, with getting a positive response. The point that BMW has not had enough complaints on this issue is beyond silly. Yes, I have complained and called and written. If you go to any older 5 series and look at the windscreen, 8 out of 10 will shown this problem. How can BMW ignor that? Even Japanese car companies goodwill parts on car long out of warrenty standing, I know this for a fact! I would certainly expect a high end German company to stand up and good will a $30 faulty part! Audi does, VW does, Mercedes Benz does, so what's up BMW?
Again, if anyone has had success with this issue please share the news as I'm sure it would be helpful to other owners that have this issue. If not, I fear we will be fending out hard earned monies on a worthless part that will fail in the end.