There are 2 lines. And they aren't cheap. It might be easier to find some decent ones in a junk yard. I recently swapped the right side out. They are a pain to put in and out with the engine mounts still on. I did it that way and you have to really work at it to snake the line into position. You'll likely want new bushings for the hardlines and you might as well replace te flex lines going from the hardlines to the cooler. Be very careful when removing them, dissimilar metals and all that. I've read lots of posts of people breaking things on the cooler.

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'84 300CD Turbo 132k (Anthracite Grey) - WVO - My daily driver - Recently named coo-coo-coupe by my daughter.
'84 300D Turbo 240k (Anthracite Grey) - Garage Queen
'83 300D Turbo 220k (Orient Red) - WVO - Wifes daily driver

I'm not a certified mechanic, but I did stay at a HolidayInn Express last night.