Fuel Return Line Leak Off O-ring Seals

Aqua Puttana

Poly - Thread Finder
Apparently MB has upgraded the parts Thanks goes to Vanski. :thumbup:
I’ve found MBZ dealer pricing for the new, stainless, version to be competitive and given your timeline may be worth checking with them..

Some general information.


See also
Budget friendly Return Fuel Line Hose&Fittings?

Note: Begel Germany is a company name. It is not a manufacturer located in Germany.
* OEM Code : 6120703032
* Engine: OM602,OM611,OM612 Engine: 2.7L 2687CC 165Cu. In. l5 DIESEL DOHC Turbocharged
Mercedes Sprinter Common Rail Diesel Injector Leak Off Pipe Connector Kit 5 Cyl OM612 OM647 BG07035

Metal fittings for 4 cylinder (4 out of 5 ain't bad... especially 4 metal ones.)

Sprinter 2002-2006 Diesel Fuel Injector Line with Metal Connectors # 6120703832


Stumbled upon this.

The dealer sells them, about a dollar or less a pop.

O rings
A 000 078 9381
Finally success! I've been fighting the leaky return lines for at least six months...when it first started I bought a kit of lines and fittings from a ebay source...still leaked some and I noticed that the fitting would just slide into the top of the injectors. That kit used plastic fittings so I bought a set that used metal fittings....same result and actually started leaking worse! Bought the orings that AdrianD recommended from another ebayer in the UK and problem solved! I actually had to "pop" the fittings into the injectors...thanks for everyones help...hope this helps someone else...
Bosch Common Rail Injector Leak Off Connector O Rings / Rubber Seals x 6

It's in the UK but shipping is quick and cheap.
Well i went and bought a replacement return line kit just to get an o-ring. Bought an aftermarket set up used for the duramax bosch injector set up. Was told by Williams Diesel out of Ocala that the bosch part number for return line set up on the Merc/dura match up......so in theory they should be the same. Couldn't buy anything for merc though as it is apparently only sold in europe(replacement kits). Gotta go through the dealer here in the states. That's what i was told anyway.

I mention in theory because the replacement kit i bought the o-rings look super small. Granted its been a minute since i had my head under the hood with the merc stuff in my hand, but the parts just struck me as small when i opened the package. Either way this is the most expensive o-ring i have ever bought.....bought the kit just to measure the o-ring. So now i'm hoping the parts i got are the right size and i'll have em on hand should i need one, or more. Plus now i can go source my own o-rings instead of having to pay the dealer 100+ bucks to get an o-ring. They don't sell them individually, or even in a 6 pack.

Sooooo, the o-rings i have in my possession, which are supposed to be replacement size for the Merc as Bosch part #'s where cross referenced through a Bosch dealer/servicer, are as follows. Keep in mind these are VERY small o-rings which are very squishy so getting exact measurements wasn't possible. I did the best i could with what i had so be aware that these are just best estimates of sizing.

OD----6mm or .236inch

ID----3.5mm or .137.5inch

thickness----1.20 to 1.25mm OR .047 to .049inch

This information is posted so others may utilize the sizing ESTIMATED to go find replacement o-rings without having to pay the dealer 100+ bucks for a complete return line kit. I can not vouch for the perfect validity of said sizing. Again, it is a best guess. At worst this will get you in the ballpark when looking into o-rings. When sourcing just o-rings they can be bought cheap to one can go up/down a size or 2 just to be sure they will have something in hand that will fit.

Please note: the info provided is only a courtesy of sharing collected knowledge for trying to source parts at a more reasonable price, or to not be beholden to the dealer for every little item. One must take this info with a grain of salt and not forget to perform their own due diligence. One CAN NOT take what i shared as the gospel because i have not be granted access to schematics for said o-rings. Just trying to add info the the site for future reference.

Should someone find the info to the incorrect please post up the reason why you feel it is and hopefully you will also have the corrected info to share with all of us.

EDIT----added info

Oh, and for anybody looking to replace the fuel return hose with oem stuff there is tons of it on ebay, amazon, and anywhere around the net. It is usually called cloth overbraid diesel leak off pipe/hose.... or some variant there of. You are looking for 3.2 or 3.5 ID hose/tubing.

PLUS, just found this out. The bosch siemens injectors seemingly use the same size o-rings on the fuel return. And there are tons of ebay sellers on ebay.uk that sell not only sets of o-rings, but also the brass connectors should one have the plastic ones and care to replace them as they are prone to cracking. Wish i would have found this out 2 weeks ago.

Not associated with this seller in any way....just ended up finding all the parts i was looking for(and couldn't find) with this seller on ebay.uk but don't forget there are lots of others on there, and around europe, that should be able to source your parts from.



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Aqua Puttana

Poly - Thread Finder
Re: Fuel Return Line Leak Off O-ring Seals Fittings


Spare fittings and hose "in case".

I noticed this 4 cylinder part and figured I'd add them to an Amazon order. 4 out of 5 needed ain't bad as an on hand spare.

When they arrived there were 4 tee fittings and one 90 degree end fitting. A complete set including hoses for a NAS T1N 5 cylinder.

To be clear, I haven't used these. I ass-u-me they will properly seal. (Some members have reported problems with aftermarket fittings/O-rings.) They are metal, but not brass.

Diesel Fuel Injector Line overflow hose Mercedes Dodge Sprinter 4 cyl OM646 OM611 BG07032

Dead link now.
Search using "Diesel Fuel Injector Line overflow". Amazon may not be a good option for these parts. Check reviews before purchasing.

:2cents: vic
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Aqua Puttana

Poly - Thread Finder
Metal fittings alone may not guarantee success.

I hate to say it, but I went to run the engine for the first time since installing these [brass material? fittings] metal clips today, and major leaks. I put the original plastic back in- no more leaks.

I don't want to 100% blame the product until I can take a few measurements and verify that I have everything seated correctly, but thought I'd let you know as soon as I could that these may not work. Sorry
As always clicking the blue arrow icon within any quote box will take you to the original post/thread.

There may be more updates for the metal fittings.

If different O-rings are needed Buna-N aka Nitrile rubber is good for diesel oil/fuel (-40 to +225F). HNBR Nitrile rubber has a higher temperature range.

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Aqua Puttana

Poly - Thread Finder
See also
Budget friendly Return Fuel Line Hose&Fittings?

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