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  #1  
Old 11-28-2003, 11:57 PM
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High Oil Consumption

I just purchased a '94 S350D with 140,000 miles on her. The car was previously owned by my in-law’s neighbor - who has since passed away so there is not much history I can get mechanically on this car. The car looks wonderful, but this is my first experience with a diesel.

The price warranted me taking a chance on the car. I noticed a small oil leak from the head gasket when I bought it. I have since had the head gasket replaced as well as the valves & valve seals replaced. When the head was off I could not see (from the top anyway) any pistons out of round. I did notice that #1 & 6 pistons showed some sign of oil burn off.

There is no external oil leak that I can see, but the car is consistently using about a quart of oil every 500 miles (Mobil 1 15W50) for 3,500 miles - then I switched to Mobil Delvac (currently 3,000 and counting). I have to be burning it up. There is no visibly raw oil blowing out the exhaust.

I have heard some stories about the 603 engines having problems bending rods. I was concerned about the pistons ovaling out & possibly causing the oil to seep up and burn off. Is anyone aware of any audible knocking or tapping that might occur during this process? What are some signs if any prior to failure? The car sounds & drives perfectly to me (or am I just in denial). I don't want to spend big $$$ in diagnostics - I am hoping to narrow down the search.

My next step (unless you guy's talk me out of it) was to look into the turbo. Can worn Turbo seals account for that amount of oil usage? What should that repair cost?

A bit of history - I drive about 90 miles a day - mostly highway so figure 75-80 MPH. From a dead stop or engine downshifting I can visibly see puffs of smoke. Don't know if this is normal diesel smoke or oil - How blue does blue smoke need to be to be considered oil burn off? Logic seems to dictate the smoke must be oil because I need to keep adding.

Any ideas or comments would be appreciated.

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  #2  
Old 11-29-2003, 01:29 PM
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I hate to break the news to you, but chances are very, very high that you have some bent rods, and your cylinder walls are now ovaled out. If you have new valve seals, that's not a likely cause. I had a dislodged valve seal once - if I let the engine idle for 60 seconds, then revved it, it would blow a could of blue smoke. But when driving the car, no smoke - only after idling for a while (like at a stop light). If you're getting smoke under load, it's probably going past the rings. It *could* be the turbo but that's not as likely. A turbo rebuild would be ~$500 plus labor to R&R. FWIW, only the OM603.97x engines (3.5L) have the problem with bent rods.

Here's a link with some more info on the problem. It applies to ALL S-class diesels between 1990-1995 imported to the USA:

http://www.mbz.org/info/complaints/350SD/

Let us know what you find out...
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Old 12-02-2003, 05:35 PM
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Thanks for the feedback - although it seems a bit scary.

The link you provided was very informative - (did anything every happen with the threatened class action suit?)

Would the issue of bent rods be silent when running. Most of the symptoms listed on the link were visual (smoke, oil consumption, sputtering idle...)?

Still a question on the turbo seals - how much oil could a bad turbo drink? Knowing my driving pattern - what would you guess in turbo consumption (if this was the cause)?

Notice my avoidance of the probable big problem?

Anybody interested in a S350 "Project Car"? Or a choice of parts?
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Old 12-02-2003, 06:02 PM
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I may be interested - email me.
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Old 12-02-2003, 06:21 PM
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The symptoms can be pretty silent, AFAIK, until things get REALLY bad - then power drops, it smokes black and/or blue, MPG drops, and oil consumption skyrockets. I don't think you're quite there yet. Bad turbo seals can suck a decent amount of oil but that's not terribly common. "Good", tight OM603's should be 4-5kmi/quart or better, in my experience. I'm not entirely sure how to test the turbo other than replacing it. I still doubt that's the problem. I wonder if a compression test would be helpful in this instance? Hmmm.

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Old 12-02-2003, 07:04 PM
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Bad turbo seals can suck a lot of oil but you'll see it. My truck blew the turbo seals and blew a gallon out in about ten miles.... I definately saw that. I doubt that's your problem. Have you read this post? Oil consumption 602/603
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Old 12-02-2003, 07:11 PM
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gsxr,

In the photo you posted in the above link, what's the deal with the area around the injectors on the used head? Did they have a bad spray pattern or is that normal?
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1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k
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Old 12-02-2003, 07:30 PM
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That's normal, AFAICT. That was the old head off my car. It was running perfect other than having high pressure in the cooling system after it cooled off, which is a sign of a cracked head. I pulled it off and found a few hairline cracks. But the pattern you see is due to the precision holes in the bottom of the prechamber.

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Old 12-02-2003, 07:36 PM
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What's your price? Shoot me an email. I'm in Jersey.
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  #10  
Old 12-02-2003, 07:36 PM
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I guess I've just never noticed that in pictures or maybe I've just seen pics of DI engine heads.
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  #11  
Old 12-02-2003, 09:46 PM
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Lots of people will be interested, including me. However, in the absence of signs that your engine is really bad, I suggest that you try this first: run the car with the oil level at the midpoint level on the dip stick. MB says that if the oil is at the full mark on the dipstick, the car is overfilled. Try it for a few days and see what happens. PM me if you still want to sell.
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Old 12-03-2003, 11:31 AM
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That's an excellent point. I don't add until it reaches the "MIN" mark. The marks are not "Full" and "Add", they are "MAX" and "MIN" and the correct level is really in the middle! Some engines will burn off that top quart awfully fast and then barely use any after that point. Thanks for reminding me about that, Nap...
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Old 12-08-2003, 12:41 AM
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Question oil in coolant

i recently overheated my 350sdl, and my 1st thought was a thermostat. when i opened the hood i noticed jelled oil oozed out of the top of the radiator seam. i looked in the coolant resevoir and there was jelled oil in there. But the oil looks fine, no coolant mixed in the oil or oilpan. So now i'm thinking headgasket. My freind pulled the head off and the head gasket looks fine. i sent the head out to be checked for warping or cracking. so far its not warped so bad, only 4-5 thousanths (not enough for a head gasket. they are checking for cracks in head tomorrow. pistons all come to top , flush. and cyl.'s are not out of round.

Has anyone else ran into this where oil is in the coolant system BUT NO coolant in the oil system?
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  #14  
Old 12-08-2003, 02:01 AM
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Quote:
Originally posted by gsxr
The marks are not "Full" and "Add", they are "MAX" and "MIN" ...
Gee, Dave, every chance you get you have to remind me

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