No, they don't have to be. Mercedes has that the O-rings are the same 6mm something size. So it is not wrong to use the same sized rings.

I don't know about on other forums the 7mm one in the upper position has been done by more than a few of our forum members and myself and it also works.

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84 300D, 82 Volvo 244Gl Diesel

Well, there is the name that the parts place calls the part and the name that Mercedes calls the part. The problem is that if you look at Mercedes printed manuals sometimes the part translation comes out a different name from what is in another part of the manual.

I find it best to find a parts site that has the exploded views of the parts and find the Mercedes part number and use that number and description in my searches.

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84 300D, 82 Volvo 244Gl Diesel

Yes, they're supposed to be two different sizes, also yes most folks (even those who can't properly adjust wheel bearings) use two of the same, I try hard to be a better Mechanic than that so I'll see what transpires ~ I spotted a red synthetic O-Ring assortment the other day and will see the next time I do an oil change if it's the correct ones or not .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I have many Harbor Freight O-ring kits - SAE, metric and nitrile (buna-N), HBNR, and Viton, plus an older large U.S. red-box kit. I've never found the HF O-rings to be defective rubber, but can't say how many times I've revisited an installed O-ring. More commonly, I find old OE nitrile O-rings in my older cars which have become hard and brittle.

I recall putting Viton O-rings from the HF kit on the oil filter shaft of at least one of my 300D. I think HBNR is superior to nitrile, and probably easier to source than Viton. Most consider HBNR only for AC, but if they survive that hot oil environment, they are fine many other places. Nitrile O-rings don't last as well in current AC oils like PAG and Ester.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

Look at the attached picture and I will let you decide.

https://www.ilcats.ru/mercedes/?function=getParts&class=1&catalog=68L&aggtype=FG&model=123153&spmcatalog=67K&spmaggtype=M&spmmodel=617952&group=18&subgroup=045&imageNo=2&language=en

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

There is nothing to decide. The two o-rings are identical.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

You guys are the best ! .

Thanx for the part image , also thanx Bill, I was wondering which formulation to choose, now I know .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I knew that but I also knew that you could use the 7mm O-ring on the upper one and I do that.

The first time I changed the stock O-rings I also wondered why they are both the same size when the upper one goes on a larger part of the tube. I mean on other items it is totally logical. On other things bigger normally needs a different dimeter O-ring.

At the time 2008 I did a lot of checking and found everyone was selling the stock size, so I just figured Mercedes machined the housing to work with the same sized rings and life went on.

Later I found out some members used 7mm O-rings on the upper one and that it worked so I started doing that. Either one works. When someone does a do-it-yourself mod you just have to decide if you want to try it or not.

If you buy the Dorman O-ring assortment kit using the 7mm O-ring with the stock 6mm sized ones give you 12 sets of O-rings (if I remember correctly there is 12 of each in the kit). If you changed those O-rings every 2 years you have enough for 24 years.

Best wishes.

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84 300D, 82 Volvo 244Gl Diesel

The big metric o-ring set from HF won't work. They're off-sized, really I think they are SAE.

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1985 300TD 1981 Scirocco 1.6D conv 1986 Golf 1.6D 2003 Golf TDI

So what is the “official” size (OD x ID) for each?

I don’t have any in stock, and may do a McMaster buy of a superior material (as well as o-rings for the stop levers on various 60x IPs) like HBNR for all of these.

I know the 616/617 mechanical gauges can get a bit fluttery when the rings get old/hard/shrunk, so I’m not opposed to trying the dual sizes next OCI.

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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (116k)
1991 350SD (206k)
1991 300D (228k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (267k)

Past Diesels:
1983 300D (228K), 1985 300D (233K), 1993 300D 2.5T (338k), 1993 300SD (291k)

I went to the trouble in post #6 to post the stock size and I guess you did not read it. 6mmIDx10mmODx2mmW (the W is the thickness/cross section of the O-ring).

I am not getting the material issue thing. The ones in the Doman kit from China work fine. Compared to whole process of changing the oil and filter changing the little O-rings is the easiest part of it.

You could simply us the Dorman ones and change them every filter change or every 2 years. They surely will not be hardening up in that sort of time.

If the part was something that was going to stay assembled for a long time, I could see the need for better O-ring material. But in this case the oil filter cap gets pulled out each time you change the filter making the O-rings easy to change.

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84 300D, 82 Volvo 244Gl Diesel

You are right, I missed that detail.

I’ve generally observed that those little rings shrink and harden pretty fast. My cars don’t see a ton of mileage so they see two year or more OCIs backed by UOA. Thus keeping good rings on there is helpful.

Interesting that the 617 fits a 7mm ring (so a 6mm must not seal), but I guess the design in the 602/603 is slightly different so it will only fit 6mm rings?

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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (116k)
1991 350SD (206k)
1991 300D (228k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (267k)

Past Diesels:
1983 300D (228K), 1985 300D (233K), 1993 300D 2.5T (338k), 1993 300SD (291k)

Your car and your choice.

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84 300D, 82 Volvo 244Gl Diesel

??? Of course it is. My collection is doing quite well, I’d drive any of them across country tomorrow.

Question is if the 7mm fits in the 60x, or just the 61x filter housings.

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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (116k)
1991 350SD (206k)
1991 300D (228k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (267k)

Past Diesels:
1983 300D (228K), 1985 300D (233K), 1993 300D 2.5T (338k), 1993 300SD (291k)

They come with mahle oil filters

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97 e300d, 78 300Dt, 95 E300d, 94 E320 estate