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Old 10-10-2006, 09:25 AM
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Join Date: Oct 2006
Posts: 4
Seals and...????

1991 Mercedes 350 Turbo Diesel -- I just bought it. It's fuel pump is leaking. Looks like from the top, an o ring... I am not a mechanic, I have though, been told that in order to use our bio-diesel straight, which we make to heat our greenhouse, I may need to change seals...

Questions: With or without a leak...
Does the '91 need changing before I burn straight bio?
If so, what else besides the seals?
AND... what are the new seals made of?
AND... what are they called?
AND... where do I find them?

Can you help?

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Old 10-10-2006, 10:13 AM
vstech's Avatar
Join Date: Mar 2006
Location: Mount Holly, NC
Posts: 26,286
it may be leaking due to age with the new Diesel fuel

try putting in the straight BD, it has been known to soften up seals and STOP leaking. a 91 should have no problems with BIO, but you may need to replace the fuel lines to viton for continued use of bio. I am no expert in this area, but from what I have read here, you should be fine.
search for biodiesel threads and fuel lines.
Good luck with your new baby,
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Old 10-10-2006, 02:06 PM
d.delano's Avatar
Join Date: May 2004
Location: DC
Posts: 1,466
One footnote- watch the oil consumption rate on that car like a hawk. Those cars are stinking moneypits and there is a good chance you will end up in the poorhouse. Ask around, see if what I'm saying ain't true.
'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
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Old 10-10-2006, 03:22 PM
gsxr's Avatar
Join Date: Aug 2001
Location: USA
Posts: 8,002
Eh - first, use the search tool, this has been covered recently elsewhere. Second, you need to provide more info. Is it leaking oil or leaking diesel fuel? Do you mean the fuel lift pump (which is small and bolts on to the side of the injection pump) or do you mean the injection pump itself? Sounds like possibly needs delivery valve O-rings, but can't tell without more info.

And yes, that car has the infamous 3.5L "rodbender"... do a search on that as well. It's a nice car as long as the cylinders remain round and don't oval out.

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Old 10-11-2006, 05:35 AM
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Join Date: Oct 2006
Posts: 4
Thank you... all.

It is leaking fuel. The leak clearly appears to be coming from the fuel pump. Kinda looks like the picture below. The leak can be seen when we are idling from the fourth to the left thing with the yellow top. It drove to Maine though from Indiana, just fine. Leak can't be too bad... need it fixed though. Little problems become big ones when left untended too.

Also, I KEEP using the search tool. I am finding nebul..losity(?) regarding the year or specific yearsss that the rubber issue pertains too. I am wondering if that info can be had? ie: specific actual years that the new I don't have to change seals and all to use my bio kind of rubber was used in the cars.

Also, the car came with the original leather folder with all manuals in it including a mercedes call us card... so I did. I asked about the 350 bending rod issue, they looked up the vin # stating that everything is categorized specific to the individual car and nothing came up. Am I to expect that the car I have is of the 60% that had no issue, I'm wondering. Sounds so.

You see, I am not a mechanic. I just own a new car...that I want to last as long as I can help it too. This means I probably will need to go to a mechanic. And I would prefer to be a bit educated as opposed to blind.
My experience with mechanics has been tainted with sheisters, you see.
I appreciate all assistance.
Thank you.
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Old 10-11-2006, 08:51 AM
riethoven's Avatar
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Join Date: Apr 2005
Location: Eastern Long Island
Posts: 939
Asha you have come to the right place to get a bit of an education that can save you big bucks when it comes to your car. I have read stories about people replacing major components like transmissions when all that was wrong with the car was blockage in the vacuum circuit to the transmission. Thousands of dollars vs. under $100 dollars to fix.

Having the knowledge of what is wrong and an idea of how much it should take to fix it will not only help you to avoid the unskilled parts changer type of mechanics that are getting an education on your car while you pay for it.

Regarding the orings it is across the board with all the older diesels. Since the US has recently changed to ultra low sulfur diesel (ULSD) it can make existing orings on injection pumps leak. Changing to viton orings will eliminate that problem, but I think there are also some threads talking about additives you can put in your tank to help the leaking orings.

1987 300TD x 3
2005 E320CDI
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Old 10-11-2006, 10:53 AM
gsxr's Avatar
Join Date: Aug 2001
Location: USA
Posts: 8,002
Your photo and description indicates your injection pump is leaking... the "fuel pump" is a sub-part of the injection pump, but your fuel pump is not leaking. ;-) Anyway, you need to replace delivery valve seals. All Mercedes will probably need to have these replaced if you want to use bio, and a lot of people have had leaks start with the new ULSD that's appearing at pumps now. Search for "delivery valve seals".

About the rod bending issue, just because Mercedes says you have no problem means NOTHING, lol! If your oil consumption is 2000 miles per quart or worse, start worrying. It should be 4000 miles per quart or better. Once it hits 500 miles per quart you'll get other symptoms like low power and smoking, and by that time it's too late. You could be one of the 60% but time will tell. Read this article here:

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Old 10-12-2006, 04:57 AM
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Join Date: Oct 2006
Posts: 4

Thank you!

Sounds like I should take articles and description regarding 350 engine to the mechanic when I go? The car has 189,000 miles on it. If we are not experiencing the symptoms listed maybe we are ok? I am being hopeful.

I searched 'vitol' & came up with a petroleum company. I'll keep looking.

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Old 10-12-2006, 06:45 AM
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Location: MA, VA
Posts: 363
Asha- the o-rings and fuel lines are Viton not Vitol. That should make the search easier

1989 Volvo 745- 202K
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Old 10-12-2006, 07:21 AM
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Join Date: Oct 2006
Posts: 4
haha OUT LOUD! Did I make you laugh, too? Sorry.

Yah, I figured that out this morning when rereading replies. HA


I'm finding when searching different shops on line that 1987 and earlier are there supplies for. 1991? I'm still looking.
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Old 10-12-2006, 07:29 AM
Ara T.'s Avatar
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Join Date: Sep 2004
Location: Santa Rosa, CA
Posts: 2,075

That's Fastlane, this forum's parts store. Phil owns it and his prices are pretty reasonable. That should take you to the 91 350SDL section. Always a good idea to help keep this forums going, bandwidth costs money, and money for bandwidth = me not paying a mechanic for every thing that can go wrong with my car
1985 CA 300D Turbo , 213K mi
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