the two holes on the wrist pin end are quite a bit larger than the three holes on the 300 small end. I bet they flow more oil than the three smaller ones. I don't know the significance of the other features but length of a column (which is what a rod is) affects strength greatly. If the rod is shorter it will handle a lot more compressive load.

I am no machinist nor am I an engine engineer but the rods don't clearly look cheaper to me.

Sorry to disagree. I might feel differently if I could hold them both in my hands.

__________________
[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 shorter rod might have less material and be cheaper. But I too do not see a difference in quality.
I think any cheapness, if there is indeed any, would likely be in material spec or heat treatment. But the fact that the numbers on the 350 rod are fuzzy is an indication the rod was shot peened, which adds cost.

When Mercedes doesn't take the time to make their emblem represent what used to be quality, then I surmise that they cut back and stop caring about everything else too in the 3.5. The old Mercedes company would have recalled all of those cars with any chance for having engine failure that got out the door and their engineers didn't know about the problem; unless it was intentional to keep the cars from behaving in terms of durability like the OM617.

BenzDiesel

The emblem? As a Mercedes-Benz supplier, we had certain requirements as to part identification, but not shot-peening the emblem was never a requirement.

__________________

Gone to the dark side

- Jeff

The car will drive good as you described for a long time while using lots of oil. From inside the car, you can't tell. But when people stop you and tell you that your car is "smoking" and you have to say something like "it's a diesel" because to you inside the car, the smoke is not bothering you. If the transmission hadn't failed, I would have probably continued to drive the car. I even started pouring used oil in the thing, since I knew the oil wasn't going to be in the car long enough to do any further damage. I loved driving that big Mercedes.

BenzDiesel

I hope statistics are on Striplin's side - 602s blow head gaskets. Haven't heard of a short stroke 602 bending rods like a long stroke 603. Oddly, the 190D 2.2 is the smaller 60x bore and longer stroke. No big rod bending problems there. Too bad we don't have info on the 2.9 liter 602.

Sixto
87 300D

I agree.
I was addressing a comment that the 350 connecting rod looked cheap.

But on the 3.5 this is what a bent rod does to a piston in the hole. Note the one half is shiny and the back half is oil coated. The oil coated back side is the place where the oil is escaping,

BenzDiesel

Attached Thumbnails

 

that Mercedes' supplier on the rods dropped the ball, plain and simple and Mercedes let it ride and some people were even told that it was normal for a Mercedes to use that much oil. I have a watch that looks just like a Rolex and probably looks better, but when I took the back off to put in a new battery, a made in China sticker was in the watch. I was told that it was Italian. The only difference is I didn't pay Rolex price for the watch, unlike the people who paid Mercedes price for a made in China "acting" product. Also, blue steel (which looks like was used in the 3.0 rods) is used when one wants something to be stronger than regular steel ( which looks like was used in the 3.5). Anyway, Im not so in the dark now, like I was when this thread first started and that makes me feel better about the situation. I mean I went all the way around the world looking for it not to be "bent rods", which it was all the time from the BEGINNING. I only have about $11,000.00 tied up along with a whole lot of time searching for the answer.

BenzDiesel

"I'm telling you as the picture shows and the failed engines confirm"

What do you see in the picture that confirms whatever your point is?
I doubt the supplier dropped the ball. It's Benz responsibility to assure its vendors supply parts made to spec.

I don't know if it was MB specs or the supplier, but either way, the original 3.5L rods were inadequate. The replacement rods appear to be fine. There are very, very few - if any! - confirmed reports of the updated rods bending.

It is also well-known that MB did not take care of customers with this problem as they should have... only customers who were within (or close to) the warranty period. Otherwise, MB excused the oil consumption as "normal" and refused to take responsibility. And of course they never did admit there was any problem at all, design flaw, manufacturing goof, or otherwise.

IMNSHO, I believe this was simply a symptom of the underlying problem. It was part of the change in the company philosophy in the mid 90's... note that in 1996, the first "non-Mercedes" was introduced, the W210. (Remember this car was designed years before the 1996 release!). While this may be debateable (and getting off topic), the 210 was really the first MB designed with profit at the top of the priority list, instead of reliability. Previous MB's were known to be good for half- to one-million miles if maintained well. The 210 (and others which followed.. especially the first ML) did not have a good reputation, although the powertrains were still decent. The bean counters, in search of market growth, increases sales, appealing to different demographics, yadda x 3... won out over the engineers. Sad, but basically true.

For the record, I don't at all believe the 3.5L OM603 was purposely designed to fail prematurely. However MB definitely did not do the moral and ethically correct thing for customers who complained about the failed engines (at least not without a fight - a few people were able to get some satisfaction by raising a stink with the zone rep.)

Personally I am not of the opinion that the fault lies in the rods. I believe its in the weakened block and the resutling failure between the head and block seal.

The arguement about carbon building up on the piston also rings true to me.

Either scenario does not point to a weak rod but a condition inside the combustion chamber that the rod was not designed for....either carbon build up or some kind of liquid, either oil or coolant.

I am pretty sure we have heard from a couple of folks at least who had bent rods after the "updated" rods were installed.

__________________
[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.

When you say piston protrusion... Does that mean a piston can be slightly above deck height if the rod is bent?

I always assumed the rod was shorter and would not reach full deck height.

__________________
-disav

99 E300 TURBODIESEL Astral Silver 282K - AMG brakes, suspension, monoblocks, speedo & interior - Full Load Maxed on IP by custom Speed Tuning USA Chip - T3/T4 Garrett - EGR/MAF delete
98 E300 TURBODIESEL Alexandrite Green on black leather 289K
95 E300 DIESEL Green Queen 267K SOLD
84 300D 216k SOLD
87 300D 299K #22 head - intercooler - full load adj. - 8sec 0-60mph - SOLD
76 300D 214K SOLD

I respectfully disagree, although I don't have any tangible proof to back up my opinion. Remember that the 602 is known for leaking massive amounts of oil into the #1 cylinder, with nary a single bent rod. And all these engines have EGR, again, lots of carbon chunks, but still no bent rods. A failing head gasket doesn't bend rods in any other 60x engine, why should it in the 3.5L, unless the 3.5 rods are the root problem?

I don't believe we have any concrete proof of updated rods that have bent, i.e. someone who has documented a replacement crate motor (with date & mileage, etc) and then has documented proof of a bent rod. I think there was some claims of such an incident, but no proof. However we do have lots of proof of original rods failing. I'd love to see a photo of an updated rod which has bent, complete with part number.

Normal, straight rods allow the piston to protrude above the deck by a slight amount (almost the thickness of the head gasket).

A bent rod will show a lower height, less protrusion than the other cylinders. All six should be the same. Usually on a 3.5L, cylinders 1 and 6 are bent and have lower heights than the other four.