My understanding is that combustion can occur only just so fast, thus limiting the practical maximum rpm. Diesel simply can't burn in the time allowed at 6,000 rpm, much less 12,000 rpm.

Best Regards,
Jim

For some light reading...

http://em-ntserver.unl.edu/Mechanics-Pages/Luke-schreier/unzip/Tension%20and%20Compression%20in%20Connecting%20Rods%20VI.htm

http://www.sacskyranch.com/conrod.htm

Best Regards,
Jim

I have a friend who owns a 1991 350 SD with 182,000 miles on it. He's only been driving it about a year. Recently something happened to his AC, and they quoted him $1300 to fix it. He's wondering if he should spend the money to fix this car or not. The only major repair this car has had (that he knows of) is that the head has been replaced. I'm assuming from all I've read on this forum that he might encounter the rod bending problem. Are there any other major things he can expect? What should I tell this guy? By the way, what do SD and SDL stand for?

$1,300 sounds like a complete Remove and Replace the evaporator coil under the dash, which means removing and replaceing the dash...

At this point, what other car cah your friend buy for $1,300 that comes anywhere close to the experience of driving the SD?

SD= S class Diesel
SDL= S class, Diesel, Long wheel base

Best Regards,
Jim

I suppose I should subscribe to this list.

95% sure that I have a bent rod in cylinder #1 on a brand new Mercedes factory longblock from the summer of '95. I could scrounge the paper work, scan it, and post it in the future to show and tell.

My experience about consumption is documented within the archives. This had gotten progressively worse after years as Marshall suggested.

The engine I have is supposed to have the stronger conrods, but it is failing fast. I first noticed consumption in summer of '03 of about 1500 miles/ qt. 10's of thousands of miles later, and 2 years, I can't drive it anymore. It runs, but barely. Consumption is about 100 miles to a qt at best. It has terrible combustion in #1, it nails really sharply(also needs a beltshock from the violent shaking underhood). All the while it becomes completely engulfed in half burnt oil(especially when you step on the accelerator).

I have gotten concluded it is NOT the turbo, and NOT the valve stem seals. The only things it could POSSIBLY be are the piston rings or the conrods. Something is letting that oil pass.

I am joining this little group because I ACTUALLY own one of these accursed beasts. Fortunately I have my 300SDL as well, so I am still OK for diesel transportation.

__________________
1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)

the above post seems to support the notion that the rods are not the problem.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

My stand may start sounding redundant, but if I owned one of those cars that hasn't yet thrown its rods, I'd sell it and get an S-Class diesel with a much better reputation. Also, the nice thing is that for what your friend is likely to get from selling that car (even with no A/C), he can get a 300SD in good shape for nearly the same amount. In case you haven't noticed, there are no 6-paged threads discussing fatal flaws with the 300SD! That car is as good as it gets for S-Class diesels. Digging $1,300 into that car is a risk and if he wants to take it then that's fine as well. The car could start going downhill right after that and then self-destruct in no time. At the same time, it could run for another 100K without any issues (as shown by the fact that some of those engines fail after as much as 280K miles).

One thing that I don't get is that none of the proposed theories regarding the cause(s) of the engine failures come close to explaining why the failures sometimes occur with very low mileage like 30K and sometimes with very high mileage like 280K and then also sometimes with any number of miles in between those two already mentioned, like 171K. OH WELL!!

__________________
1999 Mercedes-Benz S600, 103K miles - garage queen
1988 Mercedes-Benz 560SEL, 89K miles - daily driver
2007 Hyundai Sonata Limited, 31K - daily driver

if i ever get my hands on one like dslbnz has that hasnt blown scraps of metal all over the place i will satisfy my mind that i know what exactly happens to these engines. in other words i will be like paul harvey,now i know the rest of the story,cause i do believe i got most of it figured out now.(its a personal achievement i want to susceed at,i dont think the book will sell,lol)
larry perkins
72 old cars

larry, i am with you on the carbon being the most likely culprit. so, bottom line, though any way to prevent it?

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

At some point, I'd like to have it torn into myself. I have an ancient 1 megapixel C200 HP digital that should suffice for making the journey into the unknown.

__________________
1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)

Know it is a really long shot but try talking to mercedes about the failure of their replacement engine. You probably stand about as much chance as winning a lotto. But if not mentioning the facts to them you do not even have a ticket. The excercise might even be deemed a learning experience. You have nothing to lose other than your mind.

I am interested in this thread because I want one of these cars. This weekend I had opportunity to drive one belonging to a friend of mine. Now I want one even more.

In 2001, I spent $27,000 for a new Dodge Dakota. It's a perfectly good truck, and I haven't had a lick of trouble with it. But, it's not a "great ride".

That magnificent 91 350 sdl that might need a new engine, costing a total of $10k to $18k total (car and new engine). Seems well worth the price since they are easily classified in the "great ride" category. Gee, a new Dodge Neon is about the same price...

Anyway, getting back to the subject of this thread - is keeping the cross over and intake clean, the head gasket changed, and so forth going to prevent the soot and/or water in the cylinder that seems to be the cause of bending rods? Has anyone done these things (in process of doing other repairs) and as such, had no problem with the bent rod syndrome?

DS
87 300D
Northern Iowa

Well, the new Dodge Neon won't give you 10% of the issues the old MB will give you. There's no question that these are great cars, but don't forget that age will always bring issues that even a new Dodge won't have.

__________________
1999 Mercedes-Benz S600, 103K miles - garage queen
1988 Mercedes-Benz 560SEL, 89K miles - daily driver
2007 Hyundai Sonata Limited, 31K - daily driver

yeah, but he said it... the 350sdl is a great ride. the neon is a cheap tin can that will blow its head gasket at 35,000 miles. buy a neon and drive it 5 years and give it away. and hope nobody hits you in the rear. sure you will have lots of issues with a 20 year old car but keep after a benz and it will hold its value.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I am the original owner on a 191 350SDL. It now has 172,000 miles on it.

I have had very few problems and none that I would call serious. Leaking turbo rebuilt around 75K miles and vacuum line blocked off. Front suspension parts, 4 shocks, radiator and water pump (starting to run warmer than usual) replaced around 150K miles. A/C evaporator replaced and converted to R134 at around 90K miles. 30K services always done. Dino Oil changed at 3-4K intervals (manual says 7500).

Everything (except trunk CD player and security system) still work. No unusual engine noises to date. I am in Florida. Seems that some cars with front cylinder rod failure were operated in cold climates.

I am still able to tow a closed and loaded motorcycle trailer at 80+ MPH just fine (I know I'm tempting fate).

It is still the best highway driver I have ever been in. It has been very well taken care of and still looks great (Teal body/Palomino leather).