There is a hose you can buy, keep looking at that 56 part item, and you'll find it on various trims of the W123. There are about 4 different part numbers that apply to that item. For some reason, the EPC doesn't indicate well, what part number is superseded by another, if it is compatible or not. I had a very helpful parts person, work it out, and we ordered that same hose for $45. It is being shipped, and I should have it next Monday, I'll add here again if it fits.

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1983 W123 300TD US spec Turbo engine, with Euro bumpers and manual climate control, and manual transmission.