So I've just developed a diesel leak at the top of my fuel filter housing that has me scratching my head. There is a bolt, and under it a copper washer, and the fuel is seeping from around the bolt head and washer for the first time ever. Of course I tightened the filter, and that had no effect. I then changed the filter just to be sure and that has not solved it either. I even cut open the old filter to see it wasn't clogged and it was practically brand new (having fewer than 10,000 miles on it).

What is causing this leak??? It is almost as though I am missing a gasket or something but the unit is not missing any parts. There is just that copper washer under the bolt head. I tighten the filter per directions and have never had any problems or leakage there.

Is it possible there is an obstruction in the overflow system and the pressure is building up too high? I'm baffled.

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Where there's a will there's a way
1978 300D

Found this thread:http://www.peachparts.com/shopforum/showthread.php?t=296239&highlight=leak+fuel+filter and it should help me diagnose my problem. Out to the car!

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Where there's a will there's a way
1978 300D

Turns out I have an 01 filter with a single O ring on the shaft and a copper washer on the bolt head. The Oring must be worn out and I guess it allows fuel to leak past and the copper washer also allows fuel to leak past. I don't know which is which, but guess I will try to replace both. Don't see how the copper washer, which looks fine, would wear out?

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Where there's a will there's a way
1978 300D

Here is a photo of the bolt showing the single oring. The copper washer, not shown, lies just under the bolt head.

Attached Thumbnails

 

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Where there's a will there's a way
1978 300D

Yes, replace both.

That rubber "O" ring is flattened out and may be allowing clean and dirty fuel to mix. It's job is to keep those two separated.

The copper crush washer is a one time use item, it conforms to both mating surfaces and would need to be in the same precise position to not leak the second time.

As mentioned in the above linked post, any malleable material will work, as it needs to make a fuel proof seal on both the bolt and fuel filter head.

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83 SD

84 CD

Thanks. Does anyone know if that oring is the one listed by Phil as being for the "hollow bolt"? It's $.27 on his site. And if the copper washer is one time use, I wish they would come with the filter.

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Where there's a will there's a way
1978 300D

Seriously. Sometimes oil filters come with two. I try to save the extras.

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New, Used & Rebuilt Parts for Classic Mercedes

mbzparts.com

pick up a new copper washer at your local auto parts. You can possibly bring the old one back to life if you flip it over and/or turn it so that it can "re-crush" into a tight fitting seal... or work it with a hammer and a flat surface to bring it back to its original shape. I'd just get a new one if you can.

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

With copper, you should be able to anneal:
http://en.wikipedia.org/wiki/Annealing_(metallurgy)

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83 SD

84 CD