It's not surprising that one leaks and one doesn't. The leaky line is undoubtably the high pressure line from the pump to the raer valve and the one that doesn't leak is the return line which is under far less pressure. At a minimum you'll need to find a better patch for the high pressure line. Given what the proper fluid costs, it'll be worth fixing that sooner versus later.

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LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold