I recently had my 1991 350SD engine rebuilt as a result of having two bent connecting rods, with subsequent damage to the cylinder bores causing increased oil consumption and noise at idle.

I asked if this was a common problem at 160,000 miles and my dealer said he never heard of it before. Then I asked what I might have done to cause the problem to start with, and was told by the mechanic he cannot think of anything. The manager agreed to ask MB the question, but months have passed and I have no response yet. Is there anyone who knows if this is a weakness of that engine, or if there is something specific in running the motor that might cause the rods to bend? Why only two of six? 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)

They all did that. It's been discussed many times both
here and upon the Mercedes mailing list. General concensus
of everyone who knows these cars is to avoid them - it's easily the worst engine MB has ever designed.

Actually, yours seems to have lasted longer than most. Typical milage for failure is in the range of 75K-100K.

I frankly don't believe your dealer has never seen nor heard of this problem. They didn't sell a heckuva lot of 3.5 liter diesels, but of the ones they did sell, very many have bent rods, destroyed blocks, etc.

Try searching Mercedesshop, or try the archives of the Mercedes mailing list at http://www.mercedesmailinglist.com

Good morning, Jim --

Unfortunately, there is a history of problems with this engine and another owner has compiled some info about it at this link:

http://www.mbz.org/complaints/350D/

I am sorry to hear about your car. When I researched what pre-owned diesel to buy, every peron, web-site, mechanic and even my fortune cookie told me to stay awat from the 3.5 diesel motor.

Sorry to hear about your problem Jim...as I know its an expensive one..
Did an MB dealer do your work?...if they have serviced many of these cars they should have done a few blocks and /or engine replacements.You indeed have had a problem that has occurred many times with this engine..mostly it seems in the early 90's models.MB seemed to have gotten their act together with the 94-95 models as I have heard no one with problems with those.Your case sounds like mine...which was bent connecting rods on cylinders 1 and 6 which wore the bores and made the car burn a quart every 175 miles. I had a complete engine replacement from valve cover to oilpan.The tech told me that the new engine had tons of differences from the old....seemed the first one weren't beefy enough....but curiously some people have never had problems with this engine and have well over 200K on their cars...go figure.I also found out that MB will offer you some assistance if the car has less than about 80K.

Warren
1992 300SD 119K
Columbus Ohio
turner@greif.com

[Edited by turnne1 on 07-25-2001 at 09:08 AM]

Thanks for the information, even it is all basically bad news. I am wondering if the new rods and pistons have any modifications or can I look forward to another engine rebuild in the next hunred thousand miles? I will take this up with my dealer once I get well versed in the problem. I am not a casual customer there as I have been in the area for more than twenty years, and have brought them a number of customers.

Once again, thanks for the information, and I wish I had known about this forum when I bought the car in 1995. 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,

All I can tell you is that my tech who did my engine said there were several modifications in the new versus old engine...but as I had a complete engine replacement not a rebuild...your situation might be different.I was told that the rods,pistons and head on this engine were all modified.
There is another who has posted here who has 90K or so on a rebuild and no problems.Many people had problems with this engine before the original factory warranty ran out.In that case MB put a new short block in the car under warranty.I have not heard of any of those people having problems again.
But remember a new short block only comes with a 1 year warranty and a complete long block assembly comes with a 4 year 50K warranty
The dealer I went to said they had done a 2 short blocks there before and I live in a city where there are probably not more than 10) 90-95 S class diesels...and curiously there was another having an engine replacement at the same time I was.

Warren
1992 300SD
Columbus Ohio
turner@greif.com

He wrote a perfect explanation, but I just searched and could not find it in the archives. I think some of the early posts have been dumped. Anyway, it went something like this:


Oil seeps from the turbo bearing and forms a ball of carbon in the exhaust system. Eventually it gets big enough to break off and gets sucked in to the intake by the EGR system. The combustion chamber in a Diesel is extremely small, so the result is bent rods.

Perform a search on "Diesel EGR" and username "Benzmac" and you'll find some other times when he's mentioned this.

The ultimate solution is to disable the EGR which, of course, is illegal.

Sorry you had to go through this.

__________________
Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References

Unfortunately, I believe that there are more reasons for problems on the later 603 engines in addition to Donnie's carbon explanation. I spent about 30 minutes on the phone one day talking to one of the major independent MB engine rebuilders after we had an extensive discussion about these engines on our list. There are a number of plausible theories out there about the failure of these engines but one thing is certain: they do fail in much greater than normal proportions and are a real black eye for the history of Mercedes-Benz diesel reliability. And -- it's a shame because the long-bodied "L" chassis -- with this more-than-adequately-powered diesel is a great combination -- if the reliability and durability were up to typical MB standards.

Richard Easley
Waco, Texas

This problem with these cars I think is somewhat interesting.
The MB dealer techs are somewhat tightlipped about this....I assume as to not badmouth MB's as I have heard that Mercedes comes down very hard when they hear their products are being badmouthed by their dealers...I finally got some information from a dealer in another state that I had used in years past...that I guess trusted me not to relay his name to MB directly. I also talked to an independent that told me he had replaced the piston rings and done a valve job on a 90 350SDL and the car has been fine for 100K. Although it seems that most people...especially those under warranty went with a new short block.
I had a long heated conversation with the regional MB rep...one of the things he told me was that he has never heard of problems,nor paid any claims with a replacement engine......time will tell I guess?
Curiously he also told me I might look at a 98-99 E300 Turbodiesel(W210) as MB had paid many less warranty claims on those cars versus the S class(140) cars


Warren
1992 300SD
Columbus Ohio
turner@greif.com

Thank you for sharing your disappointing chronology.

The consensus seems to be that the engine was built with understrength connnecting rods. The head problems should have been cured by the time the 603.97 came out (first version had serious cracking problems if overheated, second version still had a problem with the head gasket blowing out into an oil passage at the front of the engine and hence into the chain case -- no engine damage MOST of the time, but occasional hydrolock from oil filling #1).

There are three versions of the rods, the last being some 90 g heavier than the first ones, engines with this rod set appear to have normal MB longevity.

MB officially denies all of this, of course.

I've heard that about 40% of the engines failed before 100,000 miles, very bad by MB standards, and if this is true, it points to a very definite design defect. I personally believe they should have recalled all of them and replaced the rods at least, but this is not really a safety issue so there is no legal requirement to do so.

They did replace a large number of engines under extended warrenty for original owners, but second and later owners get left out in the cold.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Jim,

All manufacturer's reps. pull this, "Its news to me", crap. I have had 2 Dodge mini vans and a total of 6 transmissions between the two. Weak trans. in Chrysler vans is very common knowledge among users and I am sure among the dealers yet I had a local shop manager look me right in the eye and tell me that he had never heard of this problem in the 15 years that he had run that shop. I nearly laughed in his face. Fortunately my son ran the car (190K miles) through deep water on the road and bent a rod in the engine so the car is now for sale for parts.

I used to work for an off shore oil field supply boat company and we used a lot of 1,100 hp V16 399 Catapillar marine engines. These engines had a history of bad cam shafts. All the chief engineers in all the supply boat companies knew about the problem. In fact when you got a bunch of engineers together at something like the workboat show in New Orleans each year that was the first thing they talked about.

We all went to a seminar offered by Cat to introduce a new engine. The first question was whether the new engine would suffer from the same cam problem as did the current V-16. The Cat rep. looked at the questioner and said that that was the first hea had ever heard of that engine having a cam problem. The combined moan of the group could be heard in Texas I am sure.

I think that the thing that pisses me off the most is that these reps. treat you like you are some rube that just fell off a cabage truck. If one is a mechanic he is aware of these problems becasue he has to fix them. If one is a maintenance superintendent then you know about them because you have to go to your boss and ask for money to fix them. And if you are an owner your know about them because you have to pay for the repairs. One way or the other you are not making up the stories out of whole cloth inspite of what the rep. thinks.

If your mechanic doesn't know about the 350 bent rods then he is either lying to you or is so incompetent that he shouldn't be repersenting a dealership. See if you can find a recall notice and take it to him. Better yet take it to the dealership owner and tell his that his shop super. is unaware of a rather major malfunction in a MB car.

Jim,
'Sorry to hear about your motor.
psfred and everyone else are correct ,there was something wrong with the
original rods ( + maybe the secondary sets).
I had a parts person read to me over the landline a side note from mercedes
parts 'fische "never to use the rods with the original rod part # again" .
A southeastern mercedes engine rebuilder has seen too much co-relation
between non functioning glow plugs and bent rods on these motors.
(his theory is: too much raw fuel dumped into a cold cylinder @ startup
= hyrolock...)
Many ideas have been proposed.

I have a note top myself ( too many notes , too much disorganization)
about rod(S) # 603 030 3120 , but I can't remember if this is the final
permutation of part #'s for the 603 or the 602.

FYI-Check the date on this thread. Before today's posts, the last contribution was 07-26-2001.

__________________
Never a dull moment at Berry Hill Farm.