I agree that the plastic clamps can cause lines to vibrate and start leaking (why did MB make them out of thin tubing? It look to be less than half the wall thickness oflines on the 617 engines!) but if its leaking at the compression nut it is probably due to having been overtightened, that will crack it for certain!

__________________
'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!