Two areas to check that are not obvious.

1. Leaks into the windshield washer fluid from the windshield washer heater. Anti-freeze will streak the windshield.

2. Slow leak from the auxiliary pump.

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1999 Mercedes E300TD daily driver sold at 238K miles 106K miles were mine, rust worm got it :-(
2006 Mercedes CDI new daily driver! 56,000 miles May 2016 now 85,625 Apr 2018 and Apr 2019 101,000 miles Apr 2020 109,875. March 2024 135,250