After checking a few other diagrams and knowing the line is on driver side, I started to think it was item 92 in diagram. Rowdie (who sometimes posts here and has a late model 107) also thinks it is that return line.

The hose it seems is 7.5mm ID x 13.5mm OD. It is clamped to the metal return line.

You will have to completely drain tank to remove that hose. If part at tank is still good, it could perhaps be clamped closed, cut off and a short piece of tubing used as joiner to a new hose?

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5