nah, I'm just saying if the injectors are dumping fuel into the motor, and it's not gotten black soot, then that volume of fuel would be building up somewhere. dumping out the exhaust, or finding it's way into the crankcase. I've seen that on several diesels. usually with a valve problem though, injectors usually fire and dirbble causing noise, and poor running quality.

Take a deep breath and relax. When I first got mine I was thinking the same thing. Do an oil and filter change. Change both fuel filters. Put in a new air filter.
After all that go top your tank off. If you have a known distance drive (work,mother in laws house, or hop on the interstate for 50 miles one way, something) take that drive,then figure your mileage.
When i got mine i thought that it was drinking fuel as well but it was actully getting about 23 mpg. Now that i have worked out a lot of little bugs(vacumn leaks small fuel leaks clogged oxycat) I am consistanly getting 25 mpg.

Good luck with it these are great cars.

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86 300SDL. 250,xxx on #14 Head. One eye always on temp gauge.. Cruising towards 300K

Ok guys thanks to everyone for the great advice I plan on looking everything over later today if I get a chance and see if I can find any leaks. I haven't seen anything leaking under the hood since I have owned it. I will look better now and check around all the injectors and actually get under the car too if I get a chance.

What I did do is today I was down to 1/4 of a tank driving to town and back. I remember at half a tank I drove to town and back twice and around here close to the house maybe a couple miles just going to the store and to my dad's a couple blocks away.

I drove around 75 miles from half a tank to 1/4 of a tank. So today I was thinking well if there is a big problem with the gauge or the sending unit in the tank if I put fuel in it even if it's just 5 gallons it should raise my gauge a pretty big amount. So I went to the store and I put in 5 gallons of fuel. It raised my gauge from 1/4 to 1/2 so that gave me 1/4 of a tank of fuel. So with that said because I knew the mileage I drove from 1/2 down to 1/4 was 75 miles then that should be enough proof of the mileage I'm getting. That puts me around 15 MPG so yeah something must be leaking some wheres. I don't see how you could get anymore accurate then that other then the actual sending unit or gauge giving more then one false readings. Which is possible but very unlikely.

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86 Mercedes 300SDL - 400k+ miles

Alright guys this is what I have figured out. First I looked under the car and everything was dirty but nothing was wet as if anything was leaking so that's good. So I looked around and noticed what looked like an oil leak but couldn't see where it was coming from. Sitting on the driver side engine mount. So I stuck my finger inside it and it wasn't oil it was diesel. It was black so I assumed oil but it was only black because it was leaking down the side of the motor and turned black by the time it got to the mount. I found the leak coming from the top of the pump where the lines come off to go to the injections. I will be attaching two pictures. The red circles are where it's leaking at I can see it steadily coming out. Not pouring out but at a fast enough rate I can see where all the fuel is going now!

Is there some type of gasket or o ring under those line inserts on the top of that pump? How do I fix the leak on this?

Attached Thumbnails

   

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86 Mercedes 300SDL - 400k+ miles

I've done some research after having no clue what I needed to search for and after about an hour I was able to come up with the name of the Delivery Valve so I was able to look up instructions on changing out the o rings. I see that it takes a special socket that seems to be extremely expensive. Are there any cheaper versions of the 617 589 01 09 00 socket that I can buy to do this job?

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86 Mercedes 300SDL - 400k+ miles

Don't know, but we have a tool rental program on this forum. Private owners have agreed to rent their tools to other members on various individual terms. Everyone's own risk of course. Here's the thread if you want to look:

http://www.peachparts.com/shopforum/showthread.php?t=126728

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~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

Thanks a lot man that's a genius idea I was dreading having to pay $50 for a socket that I might only use once! lol It's nice to know I can rent stuff here that's awesome! I posted there asking if anyone had one to rent.

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86 Mercedes 300SDL - 400k+ miles

I just checked to see if there are any Mercedes dealers near me and the closest one is over two hours away. Is there any good places online that I can order the o rings I need?

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86 Mercedes 300SDL - 400k+ miles

This forum operates its own parts store for Mercedes. Phil, the operator, knows everything about these vehicles. Can get dealer-only parts for us, and around here, we buy everything we can from the forum shop just to give back to the organization since we're all using the server and resources for free. Here's a link for the exact part you need; went straight to it.

http://catalog.peachparts.com/ShopByVehicle.epc?q=1986-Mercedes--Benz-300sdl-Diesel--Injection&yearid=1986%40%401986&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6212%3AMBC|1512%3AED|10000100%40%40300SDL&catid=240706%40%40Diesel+Injection&subcatid=242449@@Delivery+Valve+O-Ring&mode=PA

The store is accessed through the "Buy parts --> fastlane" link at the very top of every page on the site. Or you can call or email Phil with specific requests for things that aren't in the catalog.

There are other online shops out there (in the past I have used *********************** but lately their site has gotten almost unusably clunky) -- but as a matter of forum courtesy we try to restrict our recommendations to the dealership or to Phil first and foremost, since it is giving support back to our supporters. I can't remember if it's a forum rule or just a commonly-known courtesy thing, but either way -- I'd start there.

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~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

I have no problem at all ordering from the forums I definitely like the idea and love the forums here so my support is always there. I'll be ordering some as soon as I can get to the bank and get some money in that bad boy.

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86 Mercedes 300SDL - 400k+ miles

Seals have been ordered I'll be looking forward to getting them. Just waiting on someone to IM me back on the socket so I can get it paid for too!

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86 Mercedes 300SDL - 400k+ miles

I got my socket and o-rings in today. I got everything installed so now I'm happy. The ones in there were smashed pretty bad and had crap in between them. Pieces of dirt and stuff.

After installing I didn't really think about priming or anything considering I have never owned a diesel before. I tried to start it and took quite a few turns to get it to prime and start but it did start. It's running good but now it's smoking white pretty bad.

It never smoked as far as I could tell before. I'm sure it's just the oil I used on the o-rings or maybe some water got into the delivery valves when I had them out.

Should I be worried about the white smoke or do you guys believe it will straighten out and it's only because I busted the lines and valves loose as to why it's smoking?

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86 Mercedes 300SDL - 400k+ miles

I'd go for a 20-25 mile drive on the highway and see if it is still blowing smoke. If it is then it might be burning coolant....

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Well I'll probably do that tonight and see what happens. It seems like when I first started it up it smoked quite a bit but after about ten minutes I shut it off and came inside to post here. I went back out to start it earlier to go to my dad's and it wasn't smoking as bad this second time.

Something I have noticed though I'm pretty sure I'm not imagining things is it seems quite a bit louder now? As in the clattering a diesel does when it runs. I swear it's about as loud as a cummins now. I know for sure it wasn't that loud before.

Other that then it as a wine sound when I accelerate sounds like it may be from the transmission but I can't hardly tell. I can't seem to remember it doing that before.

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86 Mercedes 300SDL - 400k+ miles

What do you mean by burning coolant? I took it on a 40 mile drive last night and I noticed today it still smokes a little but nothing like it was doing.

It sure does seem like it's quite a bit LOUDER then it was before the o ring replacement. The clattering is pretty bad.

I didn't do any type of priming or anything after I replaced the o rings I just turned the key on, let the glow plugs work, then turned it over till it started. It took quite a few turns to start but it did start and run. I dunno if that was good for it or a wrong procedure or not!

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86 Mercedes 300SDL - 400k+ miles