I replaced an SLS line in my 80 300D Euro sedan -- pain in the butt! Is the line rotted through? If so, I'd consider cutting the bad section out, flaring the ends, and replacing the bad section. You can fine metric line and couplings online. I may have a small piece or two of the metric line leftover in the garage, but I can't guarantee that. In the meantime, are you keeping a jug of hydraulic fluid in the trunk? Many folks have used regular old fluid from a farm & Fleet or similar -- others insist that the MB stuff is the only way to go. I would think that the generic stuff would be better than dry, though!

Good luck...

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1992 300D 2.5T
1980 Euro 300D (sadly, sold)
1998 Jetta TDI, 132K "Rudy"
1974 Triumph TR6
1999 Saab 9-5 wagon (wife's)