I have a 94 e320 that's GAS not Diesel.

Considering the chassis should be "almost" identical you may be able to access the "pipe" by removing the "fake" insulator firewall and / or shroud covering surrounding the windshield wiper assembly. In the attached photo, immediately behind the engine are two pieces; a composite insulation panel and behind it a plastic panel. Lift up the rubber molding. Unscrew a few quarter size black plastic fasteners and remove the panels. You should be able to see under the Heat / AC air box. If you can see the pipe, but need to remove more panels to access it, search this site for windshield wiper assembly removal. Basically ALL the plastic covering between the fake firewall and cowl is attached by a lot of screws and two slider clips. Easy, but time consuming.

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