I suspect that part number is incorrect (MDB=WDB).
You can look up parts here:
www.slkworld.com
You can look up parts here:

LINKS toParts, Assemblies, Technical Data, Locations of...
I could not face the traffic this Holiday Weekend - So what to do ?? I've just put together a Small Web Site (2 Pages)with links on them to SLK R170,R171 & R172 Parts, Assemblies, Technical Data and the Locations of Parts. Also there is a Large listing of ODBII Fault Codes (Circa 3000) and a...