[Sneaky Pete]

If you don't mind me asking, where are you hearing this?

Probably from the same sources as me,Dutch and German MB forums. Problem is widely spread among several models, e.g. W204,W212,etc, and costs are very often,but not always,100% covered by MB. Here is a thread from the Dutch MB forum that deals with this subject. In Dutch ofcourse so use Google translate if you are interested.

W 204 Subframe achteras - MercedesForum.nl/be

 

[Sneaky Pete]

Does anyone know if the subframe design problem was solved during the life of the R171? Do the post 2008 facelift models have exactly the same subframe as the earlier years? Is it just taking longer for the later MY problems to emerge?

Does anyone know if the subframe design problem was solved during the life of the R171? Do the post 2008 facelift models have exactly the same subframe as the earlier years? Is it just taking longer for the later MY problems to emerge?

I am afraid not. And it is not only R171. Other models have the same problem,e.g W204 and W212. Even from later years like 2010. Seems more a design flaw in the subframes,allowing water to get in as said by @Slik hot .

 

[Sneaky Pete]

Just a heads up,I am now reading reports in the Dutch MB forum of owners that are proactively contacted by the Dutch MB organization to have their subframe checked at the dealer,free of charge, and if necessary replaced,also free of charge. Also for older cars,e.g. a W204 from 2008.
Don't know if this is only valid for MBNL or a change of policy for MB worldwide. Maybe someone at MB's legal department in Stuttgart had a wake-up call.......
Anyway,for those who encounter this problem,it might pay to persevere as stated by others. Don't take no for an answer right away.

 

[Sneaky Pete]

Is this an issue with the 171 only? Would assume its not with the 172, what about the 170?

R171 has the same chassis as the W203. R172 has the same as the W204. Lots of reports of the same problem on the W204 in other forums. So my guess is R172 has the same potential problem.
Don't know about the R170. That one is based on the W202. Did not hear of problems with that one.
Can't say it enough,if you have this problem it pays to persevere at the dealer. Over here subframes are replaced with a new one FOC or for a small fee even with 17 year old cars with no service history. If you have an unwilling dealer don't take no for an answer!

 

[Sneaky Pete]

For those interested,here is copy of the MB servicedocument.

It is in German,but basically it says that the regular serviceplan has to be extended with the inspection of the rear subframe for rust and corrosion holes for the models listed. Which includes,as expected,the R172.