Thank you for all of your posts. They have all been insightful. I am now convinced that there is some form of design, how should I put this delicately, oversight from Mercedes. It is my opinion at this time, that due to reputation and monetary concern Mercedes may have been less than forthcoming with information on this engine. Given my extensive mechanical/engineering background I am forced to believe that the post by Jim Smith is most accurate. There is no reason that a part, such as a connecting rod should suffer failure in so many instances, given that no other component parts have failed. There does seem to be a dearth of evidence that shows that this is the case with this engine. I would still like to know if anyone out there has any knowledge of improved rods for my 350. If there are modified or improved rods then the problem can be remedied. The only question left then is, how much will they cost and who will pay for them. Having worked before in the role of a contract negotiator I believe that Mercedes and the owners of affected cars can settle our grievances equitably. I have a part-time job working in a law office as a research analyst, and have many favors to call in if things get ugly. First since Mercedes dealers appear to be tight lipped about these parts I really do need all of your help in ascertaining if these improved rods are indeed factual and not a myth. Second I would request that all those who have had problems with their 350 engines contact me either on this list or through my email with all of their details. It is my intention that I/we receive some compensation from Mercedes in this matter. I believe that it would be to all our collective interest, Mercedes included, to see a solution to this dilemma that would bring about a robust and long lived 350 engine. Any assistance that can be rendered will be greatly appreciated. Thank you.

__________________
T.W.
1987 300D 170,000 Mi.
1990 350SDL 105,000 Mi.
1979 450SL 147,000 Mi.
1976 U 1300 Unimog 4400 H
1963 Piper Cherokee 160 1800 H

I have a 1995 S-350 with 167,000 miles. The only problem I have is what I think is excessive blowby. Have not done a compression test yet. The car was using oil (one quart every 750 miles) and I had the turbo overhauled. At the same time I disconnected the EGR and routed the blowby tube to the bottom of the car and started using synthetic Rotella.

http://www.peachparts.com/shopforum/showthread.php?threadid=25487&highlight=egr

I am now going 1500-2000 miles before adding a quart. I have heard that the later 3.5 engines had different rods and what not in them. Donnie might can shed some light on this. As I have stated before I think one of the main problems with this engine is the crud from the EGR that the engine eats. I mean big chunks of oily, sooty, black, hard, junk. Most of it goes down #1 and 2 intake runners. Where the bent rods are found. It is my theory that some of this hard crud gets eaten under full throttle and could possible bend a rod a little and start the egg shaping of the cylinder wall. Only speculation. I don't know if the '91 engines even had EGR or not. Only time will tell on my engine and I plan to keep it either until I die or Mercedes starts importing another S-Class diesel. I know I will get some flak about this but in my opinion it is the best, most comfortable, roomy, powerful, efficient (for its size) diesel Mercedes has ever built. It will run a certified 118 mph and gets from 24-30 mpg depending on how it is run. The later model E-Class is a nice car but it does not have enough room for my family. I needed the larger car.

__________________
1995 S-350
370K + SOLD
1952 220B Cabriolet
39K kilometers + SOLD
1998 E300D
310K +
2012 E350 BlueTec
120K

THE connecting rods were modified durning the 1994 model year & installed on engine number 603.971-12-013644 & later.
IF you need to replace a rod on earlier engine numbers including the OM603.970 engine ALL of the rods "must" be replaced as a complete set.
THERE have been 4 different part number changes on these rods!!
WE (dealer) have replaced at least 10 sets!

THERE are still many(most) engines with original rods that haven't had ANY problems!!

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

In the case of MB, this is not a problem because of trying to save a penny here and there like the US carmakers do. It was just an engineering oversight(blunder). Everyone makes mistakes.

Additionally, problems like this are not as pervasive as they seem. I have no idea what the statistics on this are, but if the failure rate were 10% that would be very high. When mechanical products like this have weaknesses, they will show up in certain ways under particular conditions. If the guy at the service department sees 10% of a particular product failing he automatically learns that this is a weak spot and considers this to be a less than robust model, and rightfully so.

Just because you have one of these engines with a statistical weakness it does not mean that yours is bound to fail.

Have a great day,

From what I heard in the other MB diesel list, more than 50% of the 603.97x engines fail below 100kmi. These are used on the 90's S class cars and the typical failure is bent rods and the symptom is oil consumption.

The 603.96x motor has a 5 - 10% of chance of head cracking. These are used in the 86 and 87 diesels. We hear many have had this problems (quite a few forum members have had this problem). Mine does not have this problem, KOW.

M.B.DOC,

I have been particularly harsh on Mercedes-Benz about the problem with the connecting rods, likely due to my personal experience and disappointment having to trade in such an otherwise superior vehicle to keep from falling into poverty. I am very curious about what the design changes were to the corrected or later part number rods, and which ones really corrected the problem. It seems to me there could be a number of engineering failures, from the specified base material and heat treatment, to the manufacturing tolerances specified, or even the forging sequence used by different suppliers. That not all fail in a given time period is an indication the error was not a nominal design error, but one that affects the individual rods based on some statistical basis tht is related to the manufacturing processes used. It is still an error, and the fact that it took three redesigns to get it right, if it really is right now, is not a confidence inspiring fact if you have had your engine rebuilt before the last design iteration.

After all that what I really want to know is, are you aware of what makes the new rods different than the three predecessor and original designs? This is what I could not get from the local service manager and drove me to trade the car in. I would still like to know what the changes were, and how they are going to fix the problem, just because I am curious, not because I want to make trouble for MB. They have already been reasonable enough with me on the trade in, which I suppose is a benefit of having bought the car from them to start with, and is not an avenue for others that buy them privately.

If you know the answer I would appreciate "closure" on the subject. Thanks, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

If anyone has an example of an older (faulty but not yet broken) connecting rod, and a newer (better/fixed) one to send me, I can perform a metallurgical stress analysis, to see if the new ones really are stronger (composed of different materials) and by what factor. I could have all the equipment at my disposal, depending on their size (it they'd fit). Could maybe make a lab out of it!

ATLD

I have a 1992 300SD that had a complete long block replaced about 14 months ago.....my engine was burning a quart every 175 miles according to the MB dealer oil consumption test.
The technition told me the new engine had beefier rods and a completely different head design than the older engine..also said that there was a myriad of updated design of parts such as the engine shock absorber,mounts etc
One thing I have noticed about the replacement engines(the two I have heard) is that the new engine is louder than the original...no sure why that is??(heavier internal parts?)
The engines on these cars were originally whisper quiet...you almost had to stand right next to it to know it was diesel
now the car can go between oil changes(4-5K) and not burn any oil.According to the MB zone rep they have never had a replacement longblock fail..........we'll see I guess ...I have 30K on the replacement engine and thus only have 20K miles worth of warranty left which will run out before the 34 months left will

Jim did the dealer offer you a fair deal on the trade in ?


Warren
1992 300SD
Columbus Ohio

FYI in regard to $ help.....I think MB will contribute to the repairs on cars with less than 100K and I think may cover the complete repair if the car has under 60K and you have proof that the car has been maintained (dealer records would help I think)
On the MB warranty cars(original and starmarked) the usual fix was a new shortblock...cost around 9K I think

I know of someone in Texas that had less that 70K and complete MB dealer records.MB cover his entire bill on a 1993 vehicle and another gentleman on the east coast that had a complete longblock and turbo replacement....cost around 13K...MB covered 50%...as I recall the car has 75K

Warren
1992 300SD
Columbus Ohio

Warren,

My car had 162,000 miles on it when it succumbed to the bent rod syndrome. I bought it with just under 75,000 miles and had it Starmarked. I never had any real trouble with anything during the next 25,000 miles, and I mean nothing. Thereafer I started having problems with window motors due to children playing with them and using them to give each other "rides" which is not the car's fault. And the window wiper mechanical set up failed. Everything else, muffler change and so on was "normal" and I looked forward to another 15 years with the car as it had absolutely no rust or paint damage.

To answer your original question, I got what I put into the repairs taken off the price of the car of my choice, plus the low blue book value of the 350SD, as the opening offer. We negotiated the remaining delta to what I was able to pay for the car of my choice, which was the 1998 E300D Turbo. This car was also Starmarked, and had only 40,400 miles on it. I did some comparison shopping at another dealer in the vicinity, and I got no more than the low blue book value for the car in trade, and relatively little movement on the price of an E300D they had which was listed for about $1K less (it was the same year and mileage, but it was not as well cared for by the PO as the engine compartment was grimy and filthy, it did not have a CD player, and it was white with a black interior while the one I got is silver with a grey interior, which I like better). So, I believe I got a reasonable reaction from the dealer. I know he sold my old car within a few weeks, and I am sure he got a good price. The car looked, smelled and felt fantastic.

Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Jim,
The original rods were just longer 300SDL rods & with the EXTRA load that just didn't work well. MOST rod failures that I've seem are from "LIQUID" compression. Some fluid in the cylinder, ie: bad injector OR head gasket leak.
THE new rods are thicker & beefed-up in every way possible. THAT is why MB says only replace is a complete set, because they are that much heavier. Close to 1 oZ.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

M.B.DOC,

Thanks for the input. I believe the rebuild on my car had all new rods, all new pistons, wrist pins, bearings, but no head changes and no crankshaft changes. Why the shop manager could not go over the changes with me added to my concern. Especially if the changes were so straightforward. Thicker, deeper flanges, etc. just some kind of explanation. Well, I spent a load more money to get the newer car and if it lasts a few hundred thousand miles I will be happy.

I am always amazed at the ruggedness of the 240D. I actually tried starting that car once, in the dead of winter, and it refused to start. I jumped it with one car after another. Finally, I checked the road we live on and confirmed the hill was clear of snow and I could expect to get good traction trying to push start it. Well, I got it going pretty good, maybe 18 mph, and dropped the clutch in third. The wheels locked up and I skidded to a stop. I towed it home and worried for a day that I had filled the cylinder with liquid fuel and bent rods!! I got in it the next afternoon and, with the temps a little friendlier, it cranked and started up. Blew junk out the back and then settled down and ran fine, still does about 80,000 miles later.

I am having a problem with my 190 2.3-16, which I will post in the Tech section and would appreciate any insight you might have. Thanks again for the information, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Jim,

from the sounds of your repair it was an engine rebuild......I know some have gone this route(when it was on their dime).....when cars were done under MB warranty they got a brand new MB shortblock......the cost of that is 9K....but to me the option that is the best in this situation is the complete rebuilt longblock....with mine I got a brand new head(redesigned) with the rest of the engine.....and the security of a 40mo 50K warranty


Warren
1992 300SD
Columbus Ohio

Warren,

Sounds like you got the best deal. Although I like my new car, it came with a bunch of payments for a while, and the old one was paid off. I was really looking forward to another 10 to 15 years of no car payments. Mercedes-Benz offered me no assistance with my repair. My total cost was around $7,000. No one has discussed the new head design here much, and I am curious if the new head design is really part of the final fix for this problem. Do you have any idea what the design changes to the head were?

I would have been happiest if there was no problem with the 350SD as it was an otherwise pretty satisfying car to own. In the end, I feel like I did not get abused by Mercedes, but it was the sales guys at my local dealer that helped most, not Mercedes-Benz of North America.

Have a good day, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

not sure what the head design changes were Jim.....I think the tech mentioned something about the cooling channels that were in the head being different than the old one....I know what you mean about the payments...there is a 99 E300 turbodiesel in town at a dealer with 35K.....its tempting...but due to all the work that I have had done on my current car in the last 24-30 months I think I am going to hang on to the old girl for a bit...in addition to the engine problems my car had had all the "classic" 140 problems....instrument cluster replacement,window regulators,evap core(twice),closing assist pump,front end work(updates)....my tech at the dealer says "why get rid of it..you almost have a brand new car".....I think the repairs since I have owned my car(about 3 years) are about at the $22K mark..mostly warranty..and all work done at either Mercedes of Morristown(NJ) or Crown Mercedes(OH)...so I feel like all the work has been of good quality....or I can take it to bat if I ever need to have a "session" with the regional MB rep again..lol
Warren
1992 300SD
Columbus Ohio