A pencil torch and thin brazing wire found at any hardware store will fix the crack. I have done this a number of times in the past. I still highly recommend getting a new line but for the time being it works. Better than a wobbly smelly drive!
Also yes, not having the lines clamped is absolutely why this happened and usually it happens pretty quickly. I have had three lines crack within a two week span before I realized the error in my ways.

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Dan
2005 E320 CDI - 246k
1987 300SDL TD05-16g, Herlevi pump, Elbe manifold, 2.47 LSD - 213k
Past: 1987 300D - 264k