90 350sdl
 

I look forward to reading all of your collective input and
knowledge so that I may garner a more complete knowledge of my current
vehicles. I have lurked on this list for only a few day however, I have read
the archives. Introductions completed I have a few questions to pose to you
the experts. My 350 has a rough idle, and shutters if I run the rpm to 1000 to
1500 then pulled my foot off rapidly. This quickly recovers, but is annoying.
I am not yet sure of what the oil consumption rate is however, the old owner
said " it does use oil between changes". It is my fear that I will be the
victim of the sad 350 story. Not being good at being a victim, I seek your
collective advice as to which is the best way to proceed. My thoughts are to
rebuild the engine. I understand from archived data that the number one rod
tends to bend. There was also an illusory post as to modified rods available.
I further understand, that Mercedes has a higher tensile strength head bolts
and an improved head gasket, both of which I have obtained part numbers for.
Does anyone know about these improved/modified rods. Thank you and hopefully I
may be able to someday answer some questions that some of you may have.

My 300SDL does the same, if you revv it, then sharpley let off the gas, it will drop to 500rpm, shudder then even out. I think its normal.

My advise would be to stay away from this car, if he says it uses oil between changes, it uses alot. If it only used a little, he wouldnt even mention it. Rebuild is big $$$ for this engine, unless you can get the car for free, forget it. You will have 2x what its worth into it to make it reliable.

Thats my 0.01 cent.

Same
 

I agree with the previous poster. From all that Ive read and heard about the 350SDL its just not worth it, the cost of a rebuild which is likely to be required very soon, is too expensive simply to make it reliable.

Tony

Erwin Rommel,

I get the impression you already own the 1990 350SD you described above. In that case you most likely are a victim already.

I was also an unsuspecting customer, but I bought mine from a dealer I have known for twenty plus years and got a break when the car started falling apart on me. But that was after I had the engine rebuilt there.

If I did it again, I insist on some kind of technical explanation from Mercedes on what caused bent rods to start with and what was done to the rods available for a new or rebuilt engine to make that not happen again. Then I would debate the scenarios of new (remanufactured by Mercedes-Benz) or locally rebuilt engine.

The MB remanufactured engines come with the 4 year, 48k miles warranty, while the ones done by the dealer or anyone else have a one year, 12k miles warranty. The total cost for the remanufactured engine is about $2k more than the other option, unless you rebuild the head at the same time.

My first choice would be not to own this car, if I were you. That may not be possible at this point, and depending on what you paid for it, you may be forced to keep it. Good Luck. Jim

I too am concerned about my '91 350SDL and am doing everything possible to prolong its life. What's interesting to note however is that the only place I have heard anything negative about this motor is on this forum! In fact, I’ve asked MB lead mechanics and service writers about the motor and they didn’t indicate any serious problems. There were only something like 6,000 of these cars produced and imported for each of the two model years….so few yet such a bad rap.

Mav

From the posts on that website you mentioned Bill I get the idea that there are a lot of stupid MB owners out there. For example:

She has yet to figure it out.

Another example:

Once agian they list no solution.

Other then the lack of common sense in those people's postings that seems to be a very enformitive site for people that like to *****.

I think that more people should be sent our way and make the world a happier more MB populated place. :D

True True, but since Rommel is asking about problems I guess that site would be a valid place to visit. Personally I've never been there my self, but I don't really think I need to. :)

Bill,

I checked out http://www.mercedesproblems.com and found 4 complaints about the 350SDL....4! Additionally, since the mechanics I’ve spoken with have no reason whatsoever to lie, I assume as you, that they don’t remember any outrageous problems with this motor. This tells me that they don’t see too many of these cars come into their shops with blown motors. They do see many more blown 300D’s but it doesn’t bring me to the conclusion that this motor is bad either. It’s possible that the 350’s two short model years contributed to this notion.

I’m not discounting that fact that the motor may have some design flaws. I’m questioning as to what extent. Since hooking up to the net 12 years ago, I’ve come to question a lot of what I read until I can substantiate it by asking lots of questions of the professionals.

Mav

Guys, here is my $.98 worth on the subject

There are problems that come from owner use or abuse, and there are problems that come from poor attention to detail in manufacturing and then there are DESIGN FAILURES. The majority of the blown engines in the W115, W116, W123, and early W126 models before the 3.5 liter Diesel come from a combination of owner use/abuse and in some cases shortcomings in the mechanical practices of the assemblers at the factory and in service shops. Things like ignoring oil changes, overheating and the like can lead to worn out engine components in under the usual several hundred thousand miles these engines last. In some cases the rubber on the valve seals of MB's failed prematurely, which is a factory quality control problem. Bent connecting rods due to fatigue failure is a DESIGN FAILURE. Connecting rods have a service life that requires, regardless of make, an infinite fatigue life. The root cause of the failure can be attributed to any number of possiblities if we speculate. I would rather not as the problem is a design process failure and I am not aware of the Mercedes-Benz design processes in effect before, during and after this engine was designed. In this case, the connecting rods are in fact engineered like no other cars - they have a finite fatigue life and when you reach it the rods bend.

I had two rods bend, and I am not an abuser of my vehicles. I would not have been so severely disappointed had some wear part, like valves, camshafts, etc., even rings or cylinder bores, worn to the point where repair was needed (I would have been disappointed, especially after having spent so much on the synthetic oils I used in my twenty five or so oil changes in the 87,000 miles I drove the car). I understand the fact that rubbing parts cannot last forever, and they are susceptible to all kinds of circumstances that depart from the intended design conditions.

I asked the service manager if I could have done something to cause the rods to bend and was told "no." I asked if I could have prevented them from bending and was told "no." I asked why they bent and was told he did not know. I had not heard of this forum yet, so I left it at that and had the engine rebuilt.

Once I became addicted to this site, I found a lot of information about the problem, much of it contradicting the seeming confusion about this problem I got from the service manager. I printed out a bunch of stuff from this and the sites mentioned above and went in to see the service manager. He was new, and not there when the sequence on my car started to unfold, and I may have alienated him a little as I came in armed for bear. But he could not tell me what was new or different to make me believe the design problem had been addressed by the new parts in my car.

I began to believe the problem was well known, but that Mercedes was unwilling to offer to correct the problem on several thousand cars with significant mileage over the warranty period. Any appearance of a problem that was known to be common to a design might lead to legal activities that could cost Mercedes millions of dollars if new engines were the court directed solution. So, I think a well orchestrated approach to making the record of this car seem within the range of what is "normal" was executed.

In separate conversations the new service manager, and one of the mechanics let me know they do a few of these cars every year, which is a significant fraction of the number of them they sold (although I was lead to believe otherwise). And they do them for bent rods, not rings, worn out honing patterns on the cylinder bores, or lower end bearings. I should have been a little suspicious when I brought the car in as I was expecting a valve job, and the mechanic was insisting on doing compression checks as he thought valves were not going to be the problem. The compression tests showed the piston to cylinder seal was gone in two cylinders. When the head came off the two bent rods were obvious as the respective pistons did not travel up as high in the cylinder bore as the others. Detailed measurements of the bores after disassembly showed the bores were oval. They were able to be remachined and the engine went back together, only to develop an oil seal leak in the turbo shortly thereafter.

Overall the car was a beautiful machine, and the one I had was in superior shape, exept for the defectively designed engine. I ended up being treated very reasonably by the dealer, and traded the car for a 1998 E300D TurboDiesel, which I could not have afforded if I had not been given consideration for the investment I made in the 350SD. My previous faith in the Mercedes-Benz traditional quality in design, manufacturing and assembly has been shaken by the 350SD experience, and I am looking for the new model to restore some of it. So far, so good.

I know the standard set by the M-B Diesels of the 70's and 80's is somewhat unrealistic to keep up with endlessly. For example, my daughter called tonight from Troy, NY where she is in college and it is 10 degrees Fahrenheit. The 1982 240D with 280,000 miles on it starts and runs fine, but seems to be overheating tonight. I ran her through the procedure over the phone for adding water and looking for leaks. She is parking it in the snow to confirm a water pump leak in the morning. But the car runs fine, gets nearly 28 mpg in hilly Troy, and starts in the winter with no water heater or anything. Great car, and the head has never been off. If this car needs some major work in the future, I may or may not go through with it. In any case I will always love the car and have the greatest respect for what the engineers and craftsman produced in terms of its reliability and affordability over the long haul. Even if I junk it because I can not find the money needed to restore it. It has provided great service in the twelve years I have owned it and put over 175,000 miles on it.

Anyway, the point is if you think an engine rebuild at under 300,000 miles is ok, then the the 350SD will likely not be the same disappointment to you that it was to me when mine died at 162,000. If you have one and it dies, I would be surprised if you got much considerations from Mercedes.

Jim

I can say this the 350 sdl has problems I have it. However, this engine can be nursed. You will have to bite the bullet at some point, but there are certain things you can do. Some were fabulous, but more than an unacceptable number were lemons. The original problem was not just the weak rods. The original problem was related to poor quality control with the heads at the foundry. There was a small crack at the water jacket that was not repairable because it could not be reached to rewelded. The rods (not being stout enough) exacerbated the problem because in some case liquid not steam coolant would get into the cylinder ...vapors compress liquids don't. This would cause an extremely high compression ratio that would in turn bend the rod thus causing an elipitical wear in the cylinder thus causing more oil consumption due to blow by. As long as you replace the coolant and flush the coolant system annually(oil gets in it due to this) also replace the hoses the oil tends to have fuel in it and eats the hoses from the inside out, repalce oil every 3,000. ensure that there is alwasy plenty of coolant because you will be losing some in the compression chambers and watch the crancase oil. If it is black good if it looks like a coffee milkshake you need to bite the bullet and replace the engine... do not rebuild. The cracks in the head, due to the temperature cycling ,tend to get worse thus causing coolant to get into the crank. A tell tale sign if this engine has this problem is if you see a minor oil slick or oil residue in the coolant reservoir . Many MB techs originally fixed this problem thinking it was a blown or defective head gasket. I have seen these defective heads xrayed and people still miss this crack. This engine, since 1995 out of MB is solid. Better coolant channels, better rods and a better match on Rockwell hardness between Cylinder, ring and piston. MB spent millions redesigning this engine, (a rebuilder is working with a defective block and cylinder wall which is also part of the equation) original equipment the new blocks meet different specs. $4000 to buy the car plus $5000 for a new engine if your nice to your dealer and $1000-$1500 for pull and installation with a reasonable local mechanic and you are back in business. The turbo is your only wildcard and if a turbo is driven correctly it won't wear out. Always idle the car for 45-60 seconds before cutting off the engine. Don't rev it it can get upto extremely high RPM's and then if you shut it off it it has no oil flow and is still spinning fast. One of the most important rule of the old oil cooled turbos that noone ever talks about. I would buy it because with proper records you can break even on the money versus resale and one helluva car to boot. I hope this long diatribe helps and doesn't bore the pros in this forum. Good Luck.

I think it is a lost cause. I'll take it off your hands for $500.

Just kidding. I wish the best for you.

I think the same of the Piper. Just throw it in with the 350. I'll take them both.:D

"I'd rather be flying, but if I can't be in the air, I'd rather be in the Benz."

I agree with what an earlier lister said about the MB problems site....some of those people don't make common sense on their site...I mean why would someone buy ANY 140 that ran sluggish...anyone that buys one of those has to have had done their homework...even besides the engine problems there are many things on a 140 that can cost you thousands....but even as much...not sure if you guys have looked at the used car prices of the 90-91 350's or the 92-95 300SD/S350 they seem to be holding their own despite all the things that have been said.....well maintained cars are bringing a premium(3.5 diesels) while I have seen some questionable ones sell for peanuts

Warren
1992 300SD 143K
Columbus Ohio

did the w140 S350 and the w126 350SDL have the EXACT same engine pretty much??

if the engine on a w126 350SDL has been replaced AFTER 1995 with a remanufactured one from MBZ (4 year warranty/48kmiles) will it have been changed with a motor containing the new updated parts thus resulting in a solid motor?

any more information on the mercedes remanufactured motors for a w126 350SDL would be appreciated

I think they were almost the same(someone correct me if they know more).....I think there vwer some modific ations made in 1992 and in the 1995 models....BUT if you have had the engine replaced ..they new one will have many modifications from the old


Warren
1992 300SD 168K
Columbus Ohio

Maverick,

The 350SD MOTORS were good.

Its the ENGINES that were bad.

P E H