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.
dieselcomponentsukltd
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