This, among the literally 15 other issues that I had with my 300E was the reason I finally decided to sell it. I just didnt see it worth the time and effort to put in $3500 to fix the problems on a car whose actual worth was $3000 in retail. Not to mention even lower in wholesale.
Sooner or later these cars tend to be nothing but a money pit. If you "love" this car keep spending money, otherwise, trade it in purchase a newer w210 model and use ur time enjoying while driving rather than staying home and fixing.