Mercedes E300 Diesel Fuel Leak (OM606) 1995 - Later

[cdw904]

The internet is a great source of information. However, sometimes you can't find exactly what you are looking for. That's why I want to share my findings in regards to my E300D fuel system. I am sure that many others have the same questions that I did. I hope this helps someone! I just purchased a 1995 E300 Diesel a couple of months ago. I love the car but not the typical problems that come with it; the leaky fuel lines. I understand that this is a problem on many 1995 and later MB OM606 diesels. These are very expensive fuel lines. These are the hard plastic lines that are connected to the lift pump, inj pump, fuel filter, etc... In my case, the fuel lines were not bad, just the connections were. The connections have a barbed plastic fitting that is held in place by a brass colored retaining clip. Pull sideways on this clip and you can remove the plasic fitting/fuel line. Inspect the o ring. This is most likely what is causing the leak. (see fig) The o-ring is old, brittle and flat on the sides. This allows diesel fuel to seep around the o-ring and leak. These little o-rings are expensive from Mercedes Benz... About $4 per o-ring and you will need approximately 12 if you want to replace all of the aged o-rings. I have intentions of converting my E300D to biodiesel in the future so I was looking for Viton replacement o-rings (Viton will hold up to diesel fuel AND vegitable oil... The OEM o-rings are natural rubber and will eventually deteriorate) Therfore, I bought one of the O-rings from Merecedes Benz and measured it with a micrometer. Then I when to Mcmaster-Carr.com and found just what I was looking for; Viton o-rings with the correct physical dimmensions. The Mcmaster Carr P/N is 9464K44 and they only cost $5.21 for a quantity of 50. This saved $$$ and I won't be replacing them again! This has cured my fuel leak! Have fun fixing yours. Craig

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[Bederka]

Craig,

how has the car run on biodiesel? Thinking about making the conversion myself.

Bryce

[greasybenz]

Please dont get Biodiesel fuel confused with a vegetable oil conversion. Biodiesel can be bought at pumps or made by mixing lye, methanol, and vegetable oil.

No conversion is needed to run on biodiesel, if your lucky and live in cali there are plenty biodiesel stations that sell it.

A veggie conversion is different. The goal is to run your engine off straight vegetable oil thus needing a conversion (second heated tank). To run on straight vegetable oil without chemically altering it into biodiesel requires you to heat it to lower the viscosity to the same as diesel or biodiesel.