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I am looking at an engine now where a design directive was given that there be fewer and lighter parts but with better NVH characteristics. Amongst other things, metal has been removed from certain joint areas. Fascinating.
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I recall talking to a gentleman who campaigned Porsches back around the time the 928 was newer. He was told not to race them. If he did factory support would evaporate for his team. Rod bearing 2/6 failures in the USA market and DNF's were apparently not part of a carefully groomed image.
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I love all those ads in North America about how you can pull a caravan with your S class. And how trailer hitches for sedans are factory options.
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Interesting to note Barry and Layback, as I tore down the engine from my '91 350SDL (which did not consume significant oil), and the pistons were level in the holes, but all cylinders were badly scuffed at 237,000 miles. The side-loads with the lowered wrist-pin were what I suspected as the cause, and I too wondered if this is a significant contributing factor to the ovaled cylinders and bent rods.
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1) Click the troll's user name and select "View Public Profile" 2) Just below the name on the profile page (top/left), click the "User Lists" menu 3) Choose "Add to Ignore List", then click "Yes" when asked to confirm 4) Relax at the sound of silence. :) Quote:
"When wrestling a pig in the mud, you both get filthy dirty. But the pig enjoys it." :whistling2: |
Ah, finally, some respite.
About five or six years ago I designed a windage control setup for the SRT4. Ed Peters (ex Chrysler failure analysis engineer) got one for dyno testing and insisted on paying for it. He carefully tested it at an oem level in his dyno cell. His comment: "this setup is the most significant bolt-on change for oil and windage control that [I have] witnessed since 1986" There is hope for a philosophy major after all. ;) Edit: future readers of the thread, please do not let yourselves be browbeaten by some of the members here ... :rolleyes: That they choose not to look should be of little import. Quote:
An inverse problem exists and many other theories can apply. There is great value in taking the time and effort to follow these alternate chains of reasoning. One never knows when circumstances will let you once again see an old friend. Good luck. |
I have a 1991 350SD. Due to the high compression & poor design of the rods the engine blew 8 years ago. MB is aware of the problem & redesigned the rod to handle it.
MB paid for the repair. I now have 303k on the car. (The engine failed around 180K) I do Turnpike driving a lot in Pa. & cruise around 75-80mph. It runs great but uses a qt. of oil about 600 miles. |
My 200,000+ mile 603s never use more than a quart per oil change, sounds like your engine is again failing and might have a bent rod or two (or just ovaled cylinders). A 120,000 mile engine should not consume oil.
Did you buy the car new? |
What year was the motor replaced?
-J |
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Bending rods due to manufacturing tolerance issues?
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"Rodbender" rods being victims of tolerance issues during their manufacture -possibly explaining why some are weaker than others -is an interesting idea. In my line of work, I have encountered fabrication problems caused by a general lack of understanding of GDT (Geometric Dimensioning and Tolerancing) -a fairly recent dimensioning system that has been embraced gradually by industry in the last Twenty years internationally. My experience has been that when an Engineer/desinger first starts using GDT on his drawings it throws Manufacturing through a loop, often resulting in bad parts. The problem is also often compounded by the fact that Quality Assurance may also not understand GDT -resulting in bad parts passing inspection. GDT is a very good system once it is understood by everyone in the Engineering/Manufacturing/Inspection chain -but learning it can be difficult -and for those without strong spatial understanding, it may never make sense -but of course, those without strong spatial abilities probably should NOT be working in the Engineering/Manufacturing/Inspection chain anyway -but you'd be surprised how many there are who do. I wonder if the design and production of the "Rodbender" engine coincided with Mercedes Benz's initial incorporation of GDT, and the inherent teething problems that often occompany it? |
Does GDT include designing for the dynamic environment? I get the sense that the rods were incorrectly designed rather than incorrectly manufactured.
Sixto 87 300D |
No -GDT is a newish ('80's) dimensioning and tolerancing symbology used on engineering drawings, that allows Engineering to communicate a "real world" (circular and/or geometrically interdependent, etc.) tolerance envelope to Manufacturing that the old "rectangular" system (+-.060, +-.0015, etc) could not. It is complicated, but is very well thought out and extremely effective.
It's a language for communicating the intended design -not for creating the design. Initial incorporation teething problems -mostly due to people simply not admitting that they don't understand GDT -can be at any and all levels of the Engineering/Manufacturing/Inspection chain, and are often never admitted to -even years later -for personal pride reasons, and eventually swept under the rug. For this reason, Management may never find out why something didn't work out -and the official explanation will become simply "something happened" -kind of like in the case of the "Rodbender". That's at least been my experience here in the US -Germany may be different. . . |
demensioning
All well and good,but, if management implements geometric dimensioning, then they ought to train everyone that will be using it or there will indeed be problems. Around "here" they "forgot" to train ANYONE on second or third shift. "you mean someone works at night?" Five years have past, still no training! Anyone here Fly? I don't! Oh yes they forgot second shift when they implemented SPC too.
Jon J at an aircraft plant in Wichita Ks. on the east side. |
There you go -Jon provides anecdotal evidence of GDT poorly incorporated -and (I deduce) in a place that makes planes we all trust our lives to. An American company goes for Five years plus using GDT without adequate training -having personally made parts from that particular company's drawings before, that sounds about right.
Seeing what mistakes a large American company is capable of incorporating GDT, could Mercedes Benz produce what looks to be one bad part, figure out it's because of a degree of misunstanding of GDT, call for more thorough training, and then sweep the whole incident under the rug? And honestly -which is the more egregious scenario? |
Head Gasket Seal
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I have been running the car on heavily fortified Elsbett SVO system (soybean wvo) for the last 40,000 miles which has involved removing the intake manifod several times to get at the glow plugs (Elsbett single tank burns up glow plugs). That intake does gum up (probably takes years). These engines can get to 110 C easy without some modification so head gasket could be an avenue to complete failure as is gumming up. For the record, I think I've posted on this thread before. I've had my car for about 145k miles and it has consumed about one quart every 600 miles this entire time, but may be worsening finally. Car runs quit well on WVO Elsbett system. |
Late 1995 S350D
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Well, rod benders, head gaskets, cracked heads, ovaled cylinders. I'm very glad I read this thread.
My Conclusion: Don't buy a car with a 60* engine. |
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I saw a previous poster who replaced a head gasket and the car had almost no oil consumption after that. I wonder if this might be the issue in many cases. My theory is that the original engine if extremely well maintained can do well. Clearly mercedes was over aggressive pushing the limits of the block in order to achieve more power for the W140. One should replace Fuel filter and air filter every year, (maybe use cetane boost), rotella t 15w40 (what I've used exclusively this whole time), and last is a big one; make sure your cooling system is modded to keep this engine 95 C and below. Every mechanic says 110 or 115 C is no problem for the block, but you also will not get as much power from the engine likely due to the turbo not putting out as much power at these temperatures. Given its history, you do not want to stress this motor. |
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If so, the application of your theory would enable you to prove your hypothesis to some degree, or challenge it yourself. Wonderful hypothesis. next question: what are all the things that have to be done to make the engine resistant to failure of this type? I ask these questions because I have a 350SDL which has a replacement engine with 60 000 on it and I'd like to do whatever is required to ensure longevity. I spend most of my time on Citorens, and I can tell you, the amateur engineers, working on the older ones, have discovered things that the company doesn't know. In the old days, at Citroen, amateurs who knew such things and passed them to company would be treated as colleagues. Nowadays, it's all about the money and few people have the interest to pursue these issues. Cars have become disposable, like refrigerators. That's why I don't drive new ones. |
The best move if you own a 3.5 is to have a spare good 3 litre engine in storage. Locating a good one while the need is not there.
The way things usually resolve themselves in life. If you have the spare engine the original 3.5 will continue to last indefinatly. Yet if it should fail you can then install a far more durable lower block. There will always be a resellers market for a good 3 litre engine if you never use it as well. |
I'm a bit heartbroken that these newer 60* engines were not more reliable. I was looking forward to purchasing a 90's model.
Which seems to be the least problematic? 606?:confused: |
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If you like power, consider a 98-99 E300 turbo. If that's not a main concern, any 1990's vintage diesel would be fine, just be aware of the 3.5L's rodbending & oil-drinking tendencies. :stuart: |
Yes, just like you should check for the weak points on a 617, or any engine for that matter, when buying a used car, you just need to keep the few niggles of the 60x in mind. When they are kept after they run great!
-J |
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Agreed. The OM60x engines are plenty reliable and the flaws are not serious (3.5L excepted). The refinements in the OM60x series greatly outweigh and minor issues when compared to the OM61x dinosaurs.
:boat: |
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:zorro: |
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...............everybody should have a little crack.........or two.............the smaller, the better...............:D |
Ok. Thx gsxr, compu_85, bustedbenz, et al. I wouldn't mind trying out a strait 6 cylinder diesel benz if I could be sure I'm not buying a problem engine.
I looked at one about a year back and it had considerable power but crop dusted the whole area so bad I hadda say no. Very nice looking car too. Pristine in all but engine. This bears some more study. Also, I wont buy one without the board's approval. Maybe I can even get Brian's blessing.:D |
FYI, don't consider an engine junk if it blows black smoke during a WOT run. That could be totally normal if it's been driven lightly for a long time. If it continues to belch black smoke after several WOT runs in a row, that might be slight cause for concern, but still not necessarily a big deal, IMO. If the car is nice, buy it, and fix the engine if necessary.
Now if it's belching blue smoke, or white smoke, that's a different story. Those are more likely to be serious repairs. But for the right car at the right price, again, just fix it. These cars are getting harder to find in decent shape, and the supply is only going to get worse. It doesn't make sense to turn your nose up at a clean chassis that only has some engine problems. Engines are a lot easier to fix than worn-out interiors or rusted-out bodies! :blink: |
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NFW a 603 will ever give you black smoke unless you got off your ass and tuned the IP. |
Seemed to smoke more the longer it ran. We had folks pulling off the road behind us just to get into fresher air. Big blobs of billowing smoke - a smoke screen even.
If you saw all the smoke, you'd have run too! See, I've already got three W123's that need fixing up. I've no need for another fixer upper.:eek: If I buy another car, it's gonna be totally cherry.:D I agree with you in principle gsxr regarding scarcity but I'm limited in the amount of space I have available. |
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I've been racking up the miles on my 350SDL. My driving habits will be a good test of the replacement motor... I'm either stuck in traffic for hours with lots of idling, or mashing the pedal. FWIW my egr is currently broken. It doesn't seem to use any oil between changes.
I've put 10,000 miles on the car since I got it in 2008, I'll post every so often with an update. -J |
What a nice old topic.
Question: 5 cylinder OM602.982 2,9 turbodiesel uses the exact same geometry as OM603.971 (bore, stroke). It comes from a 250D engine block like a .971 comes from a 300D. If this geometry is wrong, why I can't find information about bent rods in OM602.982? |
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There are many people that know/knew the specifics however they are generally covered by non-disclosure agreements that Mercedes is known to enforce in this case. |
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:stuart: |
My personal opinion is that the 3.5 engines bend rods on hydrolock after excessive block flex compromises the seal on the head gasket. A five cylinder block with all other things being equal will be more rigid than the six.
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A couple of things come to mind:
- do 2.9s have EGR? One thought is EGR crud cokes on the hotter exhaust valve so rods bend by bowing forward. - the 2.9 has one fewer cylinder's worth of influence pushing the piston onto coked EGR crud. Sixto 83 300D - |
So turning up my factory-reman .971 is a bad idea? I was thinking it'd make a nice transplant because of its tasty torque.
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A 002 140 31 60 VALVE EXHAUST GAS RECIRCULATION VALVE |
I turned up my .970 a bit (still a lower redline than a .971). The car has been off the road for over a year with other various problems though so I can't comment on longevity.
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W140.134 (603.971) A 603 030 32 20 CONNECTING ROD Replaced by: A 603 030 29 20 Text footnoteFootnoteDescription[405]ONLY REPLACEABLE BY THE SET[421]THE OLD PART MUST NO LONGER BE INSTALLED IN THIS PLACE -------------------------------------------------------------------- W210 E290TD (602.982) A 603 030 29 20 CONNECTING ROD Text footnoteFootnoteDescription[014]As of engine 980 10/50,20/60 043350 980 12/52,22/62 002281 982 10/50,20/60 001385 982 12/52,22/62 000034 |
No, small truck or SUV, wanted to put it in my Land Rover to counter my neighbor's Cummins Wrangler, ... but it is better suited for a longer engine bay already set up for a cast-iron block. It would be really nice for light towing!
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