Just a thought on the subject. A w140 with the V12 as a powerplant in comparison to the diesel s350?

I have been looking for a nice S600, and the prices have drastically fallen and I think under $20000., will buy a good one. Fuel mileage and repair costs might be on another planet, but the repairs may be similar. The cost for the fun factor may be less costly with the V12.

Comments?

You cannot compare an S600 to any other W140. They have a different suspension and drive line. An S600 will probably get mid teens on a good day but 10mpg-12mpg wouldn't surprise me. An S350D on the other hand I would expect over 20mpg.

As far as maintaince costs go V12 parts are extremly pricey, MAF sensors are about $650 each EGR's are about $500, along with all the other crap that fails. S600's depending on the year have different active suspensions. If you get a 99 you get air shocks and those are nice.

S600's are truely awsome cars but you must be willing to spend a lot of money to drive one. If a $3k repair makes you flinch look at W140's with V8's or I6's.

Now as to an S350D vs S320, the S320 is faster and probably gets slightly less mileage. Maintaince costs should be a wash.

__________________
2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

i have had an ongoing discussion with my favorite automotive machinist regarding the 350 motor. we cant figure how an engine can bend a rod just by runnig. he thinks that with the cursed aluminum head there is often a leak and one cylinder gets a hydro lock and thus the rod gets bent. this would occur after the car sits a while longer than normal and the pressure in the cooling or oiling system pushes one or the other into the cylinder. there jusst has to be enough to occupy enough of the combustion chamber to bend the rod even if it is ever so slight. the conditions to cause this may then not occur for quite a while, possibly even never again. then, with a bent rod odd wear in the cylinder, etc. occurs. so if this theory is correct, and i find it compelling, the weakness in the 350 is not in the rods but in the sealing of the head gasket. comments?

__________________
[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.

Considering all of the 350's came with the updated heads I don't think this is very likely. You never hear of any of the early 603's with 14 heads bending rods?

I think this issue is probably overhyped like the 14 head thing on the early 603's. At this point in the game these are all old cars so if has ran good for 14 years it is probably fine.

If a clean 350SD/L came along for a sane price I wouldn't not buy it because their is a small chance that maybe someday down the road the engine could blow.

__________________
2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

so forgive my ignorance... what is a 603 14 head, please?

__________________
[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.

The early 603's used what is known as a "14" head. If you look at the casting of the head you will see a serial number and in it will be a 14, 15, 18, 22. I think their are 4 heads but their might have been more. Every time MB redesigned the head it got a new number.

The head gaskets were redesigned a number of times also; maybe 5?

The 350's got the good head the 18's and the latest head is a 22.

Only the early 603's 1986-87 originaly came with the 14's. These will crack if you overheat the car. However if not overheated they will last forever. At this point in the game the head number doesn't really matter, any 14 head this old must be pretty good.

Thats my theory with the 350's, any engine that is 14 years old with 200k+ on it is no lemon.

__________________
2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

And why is that?

The rod is subject to cyclic forces that are extremely high. Accordingly, it has a finite fatigue life. If the calculated fatigue life is not substantially greater (3X) the typical mileage for these engines (300K), then, statistically, a certain number of rods will fail below 300K.

This is no different than the design of rotating jet engine parts. The parts are designed for 60,000 cycles. At 20,000 cycles, the part is taken out of service and scrapped. Can you tell which parts will now go the distance, up to the 60,000 limit?

If you can, you will be a multi-millionaire overnight.

The theory has no basis in fact. Refer to cyclic fatigue life and statistical analysis for a proper theory.

If the rods have a finite fatigue life that is "close to" the design life for the engine, a statistical number of them will fail at a point that is significantly less than the design life.

The rod must be designed with a fatigue life of about 3 billion cycles in order to assure, with certainty, that every rod will make it to 1 billion cycles (about 300K miles).

if you can show me a bent rod from your jet engine i will be convinced of your cycle theory.

my machinist has never seen a bent rod from running only. have you? they only bend if hydro locked or if something solid gets into the combustion chamber.

__________________
[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.

One of the forum members just found a bent rod on a 3.0 603 engine. Cylinder number three. Nothing solid got into the combustion chamber as far as the mechanic was aware.

Just about every bent rod can be attributed to running only.

Exactly what solid object is this machinist speculating entered the combustion chamber? Does he have any evidence of the solid object?

And, do explain why two very similar engines (603.960 and 603.970) have very different history when it comes to bending of rods. The 603.970 engine is a larger version and puts greater loads on the rods. If they were not redesigned for additional strength, they give up fatigue margin.

Cyclic fatigue is not a theory. Look it up.

Generally rods do not just bend. It takes an impact event of some sort. In a 22 to one compression ratio engine the thing that causes an impact doesn’t need to be all that big. I suspect that if fatigue were the total culprit then at least some of these rods would break not bend.

Brian, maybe you can shed some light on this for me. To me this thread identifies the most likely cause of rod bending, however I am lacking some info and have a few questions.

Carbonized oil in intake - nearest Number 1 Cylinder

Are the European 603.971 engines equipped with an EGR Valve? I hear rumors that many in Europe have experienced bent rods as well.

Second, is the EGR located in a different location on the 603.97X than on the 603.96X.
Third, is the crank case vent tube located in a different location on the 603.97X than on the 603.96X.

__________________
Don Martin
Bakersfield, CA
87 300SDL

Once again proving that MB engineers are incompetent and Statisticians are witchdoctors. Why MB doesn't let local machinists, mechanics and hot-rodders design their cars is a question for the ages. You funny. I bet you and your machinist can figure out how to beat the casinos and the lottery too. Reality sucks sometimes but it is real.

Run searches for rod bender. Some people who were facing mountainous repair bills have been through all of the stages of denial and acceptance on this one. The full ranges of emotion, superstition and science have already been covered.

I'm well aware of that theory.

The problem with it is that the theory holds that the #1 rod will bend every time in the situation described. If there is some data that shows #1 is the culprit, I'll STFU right now. The high cyclic fatigue would not be related to any specific cylinder because all loads are the same across all cylinders.

The EGR is located at the same location on the 603.970, AFAIK.

I'm not sure about the crankcase vent tube, however.

We would need input from all those who suffered a bent rod to see if a preponderance of those are #1 cylinder.

thanks for the insults... but i am not seeing you presenting any persuasive logic that disproves the hydrolock theory. you said that the idea shows that mb engineers are what, witchdoctors? i did not. i think that mb engineers are the best around. that does not mean that they don't ever make mistakes... obviously in the case of the 350 engine, they did.

i see no evidence that you understand the hydrolock concept.

obviously what is exactly happening is not all that clear. i still say that rods dont bend from just running. fatigue does not cut it in my mind. if there is a preponderance of #1 cylinder failure, that would coincide with the theory of a leaking head gasket being the problem. it does not prove it but it would be logical. i seem to think i have seen that it is predominantly #1 that bends.

comments?

__________________
[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.

The only thing I have noticed other than how incredibly nice to drive my 350SDL is ... well, is the 50% blockage of coked up oil in the intake manifold and cross-over pipe ... perhaps related, probably not?

Used to get an occasional pause with a large puff of brown smoke ... removed manifold and cross-over, dipped them about 10 times, and reinstalled with EGR disconnected ... no more ... drive better, too.

Potential "nuther theory" that junk gets into the 1 or 2 cylinders? EGR and oil fume line from valve cover are too close to one another, causing the coking?

Just some thoughts ...

__________________
George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg