There used to be a flat dog-legged wrench in all of the Benz tool kits that had a short 14mm hex on each end. Mine came in the kit for either the 190D or the 220D, so long ago I can't remember which. Don't know when they stopped including them, but keep your eyes out for the older car tool kits. This tool is very helpful, have used it to remove the drain and fill plugs for the manual trannies and the differentials.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150