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85 300CDT / 95 Accord / 07 Acura RDX
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Discussion Starter #1
Did my homework - checked some things. Read some more. Plan on purging the system of air by the recommendations in another thread - open up the injectors a little bit until I see a little diesel coming out of the very last one, to see if that improves starting.

I say that because logic tells me that air probably is the culprit since I have a leak on the bolt that attaches what I assume is the screw-on fuel filter I've read about. The leak, from what I can tell, is coming from the brass(?) bolt head. I found a photo of an engine and added me a lil red arrow pointing to what I'm talking about (still waiting on those manuals, y'all... forgive?)

That part is so specific that I don't know what to call it... I just know that it needs to be fixed, because any leak could potentially introduce air in the lines... right?
 

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1985 300CD Turbo coupe, 2006 E320 CDI sedan
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I don't actually see a question in all that. But if your spin-on filter was not properly sealed, you'd see and smell diesel fuel. It would come out from underneath the hex head and pool on the housing, and also run down the side of the filter itself. It's for that reason that I quit buying that particular filter from NAPA. The sealing ring wasn't tall enough to mate with the housing. No amount of tightening on the hex head would effect a complete seal, and flowing fuel dribbled all over the place.

//greg//
 

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85 300CDT / 95 Accord / 07 Acura RDX
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Discussion Starter #3
Ah yes - good catch. The question is: If that bolt is leaking, is it probably just the o-rings I've read about needing to be replaced... or is this a common problem with a better solution from well-seasoned, kind, and helpful Benz owners? :eek:

Gotta forgive my lapses this time of year... tax season and whatnot.
 

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2013 MINI Copper S Clubman, '84 300CD-weekend car
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Depending on what part number is on that housing, you may need a crush washer on that bolt.
The part number is 10 digits divided as follows, 123 456 78 90. What is the "78" section number? 01 or 02?

If you have an "01", that is the old style and needs a crush washer to stop the leak.

If it is an "02", you may be able to stop the leak by tightening down a bit, but make sure you have two new rubber "O" rings on the bolt, the ones you see when remove it.
 

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85 300CDT / 95 Accord / 07 Acura RDX
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Discussion Starter #5
Will double-check, but I'm pretty sure it will need a new crush washer. Will Google to find the part unless there's a specific supplier you guys recommend I use. I'm also planning on replacing the filter and O-rings while I'm at it... relatively cheap, easy, and can't hurt.

My plan of action is...
1) Get that filter to quit leaking
2) Replace the injector return lines (they feel damp)
3) Replace the fuel lines (why not, right?)
4) Open injectors 1/2 turn
5) Purge
6) Tighten injectors back
7) Try to start the car and...
8) Do the Happy Accountant Dance, or cuss a little... depending upon the results.
 

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2013 MINI Copper S Clubman, '84 300CD-weekend car
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IF you need a crush washer, they are difficult to find, so I use an item from the local hardware store, see pic.

Sounds like you have a plan, but you may not need to purge even. Replacing the return, or jumper lines, is past the combustion cycle and simply leads back to the fuel tank.
 

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1985 300CD Turbo coupe, 2006 E320 CDI sedan
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If that bolt is leaking, is it probably just the o-rings I've read about needing to be replaced... or is this a common problem ...
Well - based upon my experiences alone - I wouldn't call it common. I've got over a quarter million miles on a 26 years old 3.0l turbo, and as far as I know mine are still the original O-rings. Never replaced the washer either. The only problem I had was with the actual aftermarket (NAPA) filter itself. The round rubber sealing ring glued to the filter housing itself was too short to make a complete seal after it was spun on.. The solution was simply to buy a proper German filter. Never had a problem since.

Regarding your plan; it won't hurt anything, but it may be redundant. Get the filter to stop leaking first, then re-evaluate. If you do proceed however, do NOT loosen the injectors themselves. Just loosen the hex collars that connect the steel lines to the injectors. And FWIW, in all the Mercedes miles I've driven - I've never yet had cause to actually do that myself. On my tractors yes, but on my Mercedes - no.

//greg//
 

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The lower of the two "O" rings keep the clean fuel from coming in contact with the returned fuel. The top one seals against the very leak you describe.

I feel better replacing rubber "O" rings when they stop being resilient.
 

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1984 300D 375,000 miles 1996 e300d 266,000 miles 1983 300SD 174,000 miles Ascot Grey
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both of my cars have needed new o-rings. I got rid of the early setup on my 81, and replaced it with one from a turbo. Didn't like using the crush washer. When you look for "hollow bolt o-rings" on autohaus or partsgeek (don't know about others), they send you the small lower o-ring only. I could not find the big one, which is the one i really needed. I ended up gettin from the lowes plumbing dept, which worked very well. Don't know if they will break down over time, but haven't so far.
If someone knows where to order the actual o-ring, would love to know. I know i can find them at hydraulic shops, etc. ,but want to find it online.
 

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1984 300D 375,000 miles 1996 e300d 266,000 miles 1983 300SD 174,000 miles Ascot Grey
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ok- good- that's what i did. beautiful, bone-dry filter now, and no embarrassing ruined driveways. Also, it's nice to only put 5 or 10 lbs of torque on that bolt, like i know was probably intended.
 

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85 300CDT / 95 Accord / 07 Acura RDX
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Discussion Starter #12
Alright... will try stopping the leak first.
We have a bolt supply in town that several OTR truckers, clients of mine, use for repairs. If they don't have it, they can make it... will go there for the crush. Will use the universal O-rings as suggested. Ordering a German filter per suggestion, too.

Now... back to countin' dem beans.
 

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1984 300D 375,000 miles 1996 e300d 266,000 miles 1983 300SD 174,000 miles Ascot Grey
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one more thing (and thanks to rmac for articulating this for me a while back)... if it has two o-rings, it does not use a crush washer. I have seen where they leak, and the owner thinks the washer is missing, and adds one, which only makes it worse. If it has one o-ring, then you use the washer, two o-rings, no washer.
 

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85 300CDT / 95 Accord / 07 Acura RDX
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Discussion Starter #14
I appreciate y'all more than y'all know right now - thanks for the heads up about the o-ring/crush washer.
:bowdown:
 

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2013 MINI Copper S Clubman, '84 300CD-weekend car
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You're welcome, glad we can be of assistance, that why this forum is here.
 

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Discussion Starter #16
I just hope that, one day, I can pay it forward. I plan on making the digital camera my best friend to document steps of everything I do along the way. I'm somewhat of a nerd when it comes to that... the reason I was able to get as much as I did for the 2000 Honda Accord I traded in on the one I have now was because - as the only owner - I maintained an Excel spreadsheet with three tabs... fuel economy (measured every time I filled up), maintenance schedule (scanned in all of the receipts/invoices/etc and saved 'em), and one for minor repairs (wiper blade replacement, bulbs, etc). Maybe it's too much, but the dealer smiled.

I'm thinking my input in the future, here, will be more along the lines of... "Hey, just be sure to do XX because I didn't and let me tell you the headache it caused because I didn't!"
 
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