Welcome to the site!! IF the E350 is the same way with the water separater drain valve, then you can get a new valve with2 o rings from the dealer for 80ish dollars. It 4 screws and youre done. OR you can just get the orings and rplace them. Same 4 screws come out, but you just reinstall your valve. 30 minute job if youve never done it. Hope this helps.