Your fuel thermostat can be replaced with a kit that is sold. You can also try to find a used one or just bypass it. Unless you live in a cold climate it isn ven neccassry to have. You definitely want to take care of that leak...it only gets worse.

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1995 E420 152k
1991 300D 2.5 348116 daily driver
1992 300E 2.6 196k-work in progress(head gasket)
2002 BMW 745Li 93k