Unfortunately, or fortunately, there are no Airworthiness Directives telling when the rods should be inspected, and little or no data as to when or why they fail.

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Gone to the dark side

- Jeff

That's exactly the nature of fatigue. They cannot be inspected to determine if they are nearing the end of their fatigue life. A typical jet engine needs a factor of safety of 3:1 based upon the design fatigue life. If a component can typically go 60,000 cycles before failure, it's scrapped at 20,000 cycles. This is unpredictable nature of fatigue.

WHY NOT? any experience with this?

Just aksing not flaming!

thanks and regards
Steve

I bought them through my machinist. Thay are part of the Federal Mogul group, there is a Fedural Mogul logo on the label on the box.
P/N 87-743107-40 bar code numbers: 4 044197 004669, made by Nural, The "U" has the 2 dots above it. There is a MBZ number on it too- separate sticker- 603 030 17 17. Then BD08C. they have Goetze rings fitted, LAbel also states: "Nural and Goetze are trademarks of the Federal-Mogul Corporation"

Then in handwriting 948.7 this is the weight in grams of the piston,pin, and rings, HEAVY!

IMHO-As far as the rods go, I believe they are just weak for the application. remember that the 3.5 603 is basically an enlarged 3.0 603. MBZ increased bot the bore and stroke on these engines. Heavier pistons and larger stroke, I just think that the rods were not strong enough for the application. The new rods I got from MBZ dealer were almost twice a thick. BTW I have my old rods if anyone wants a picture.


FWIW-My 87 300SDL had the 3.0L 603, GREAT engine, had 380kMs when I sold it and use 1 liter of oil approx 5 miles. It was teh EGR then why didn't it happen on 3.0L? I feel that a piston or valve would have cracked or broken before a rod would have bent.


BTW- I got the vacuum lines all sorted out , I bought the MBZ CDROM it is very good!! Car runs EXCELLENT- lots of power, still need to fine tune the tranny shift points and adjust the max speed limit on the the IP pump.

Steve

i believe the block is already weak and flexes too much....causing head gasket sealing failures.

tom w

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[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.

Yes, I did a head gasket on mine last year before I rebuilt this year. Mine was using oil at that time also. With or with out an oil leak.

BTW both the block and head on mine were well within tolerance for flatness when I rebuilt it so neither needed surfacing.

the car run awesome with a fresh engine that is not using oil and blowing smoke!!! :-) fast too!! for 5000 lb W140 with a diesel!

Steve

mind posting pics of an old rod... my friend with his 350SDL would like it(ill email it to him)

As you can see the rod bent primarily in the side plane. In the side view it has a mild "C". There is no visible twist in the rod.

The engine actually ran very well. However it did smoke and used 4 liters of oil for every tank full. Because of the smoke all the time, including idle it would not pass emissions testing here in Ontario. For light duty diesels the test is a visible test for smoke at idle and at a certain RPM.

It had approx. 300,000 kilometers on it at the time of rebuild . It started using oil at approx. 180,000 or bit before.

The piston also shows a heavy "scuff" mark where it was pushed against the bore due to the bent rod.

The new rods are almost twice as thick as the old rods. When I find my pictures of the new rods I will post them.

In the rebuild I replaced the pistons and rods. Block bored +0.5MM, and had the rotating assembly balanced. the crankshaft just needed a polishing and was good to go.
New Oil pump, all new valves and guides, valve springs, lifters, camshaft, Timing chain and oil pump drive chain and gear. All chain tensioners and platic chain guides All torque to yield bolts were replaced. IP and injectors were resealed/rebuilt. New motor mounts, , water pump , rad hoses, etc. I have approx $10,000+ CDN in the engine alone: parts and machine work. I assembled the engine.

I also had the trans rebuild for $1500 CDN.

But it does run very good. Really smooth, much smother than before and quiet. No oil consumption so far, @ approx 500 kilometers. No oil smoke at idle or underload.

Steve

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steve i sent you a private message.
larry perkins

on doing my own work; my 3.5 wouldn't be getting fixed although a $10,000.00 investment in one of these cars and the oil consuming problem was SOLVED, would be a great deal if you had the money to spend and the nerves to take the risk.

Anyway, my 3.5 consumed two 1/2 to three quarts at 630 miles on my last test drive. That is up from less than 200 miles on two to three quarts before I replaced the head gasket and up from 450 miles on my last test prior to the 630 miles test although on the 450 miles, I added oil before the light came on. The 630 miles test was from full to caution light coming on. I've driven the car about 2,000 miles or so, since the work. The important thing is to note that the oil consumption is REDUCING and at 630 miles per three quarts of oil and the car BURNS UP the highway like it does and the oil consumption appears to be reducing; I can just about live with that for a couple of years with no problem, easily.

Right now, I've come to the FINAL conclusion that the EGR in addition to the turbo's re-design (somehow) caused the carbon buildup in #1 and #6 cylinders and in addition to breaching the head gasket, the rods bent/tilted toward the buildup on the exhaust valve as a result of the continued POUNDING of the piston on the caked up carbon on the exhaust valve. THEN, after enough carbon was formed in the cylinder; THE OIL RINGS STUCK, causing the oil consumption problem. Therefore, I am in the process up using "snake oils" to see if I can get my rings unstuck, IF they are stuck like I suspect.

By the way, if the stuck rings aren't the problem and it takes straight rods to solve it, I am contemplating the feasibility of taking my BENT RODS to a machine shop and ask them if they could heat my bent rods and put them back straight and then put some re-enforcement heat on the rods to help them from bending again before the next 80 to 100 thousand miles or hopefully longer. Has anyone ever heard of fixing bent rods?

Finally, I sure wished I could solve my bent rod problem in dieselsteve's fashion. He left no stone unturned.

BenzDiesel

Wow. From 50-60 miles per quart up to 200 miles per quart, and that's "good"? Ouch.

I still don't buy the carbon theory. The original rods were too weak. Period. The way the intake is designed, if it were EGR related, I'd expect cylinder #2 to be the frequent bender, not 1 or 6. And definitely not 6, ever. The fact that 6 bends before 2,3,4, or 5 kind of rules out the timing cavity gasket blowout theory too.

Maybe we should just accept that fact that the original 3.5's are flawed, take a lot of money to fix, but once it's fixed properly it's cured? And stop trying to overanalyze why it happens? Just a thought.

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Check out my website photos, documents, and movies!

Agreed. However, they were flawed with regard to insufficient fatigue margin. If they were flawed due to basic compressive strength calculations, more than half of them would fail the first time the engine saw 4500 rpm under heavy load.

Since the failures are somewhat random, fatigue plays the major role, IMHO.

We get 20 miles to the gallon of gas and be happy and most don't be driving a car half this nice. So 200 miles per quart of oil and IMPROVING (at this point) is tolerable. What am I to do? Throw the car away? Some people on this site say you can even make your own fuel for these kind of cars.

Edit: Maybe we all should go out and buy brand new Mercedes Benz cars and solve the problem altogether. Once the warranty expires, we can then get us another brand new Mercedes.

BenzDiesel

I have never driven a 3.5 but my 3.0 is soooo much stronger than my 82 300D that I think you will be happy. I hear that the 3.5 looses all the extra HP to the emisions systems.

significant as going from a 617 to a 603. I don't knock the 3.0 and have one. My 3.0 is not quite as fast on the top end as the 3.5 and also is a little bit slower starting from a stand still. Also, the 3.0 gas pedal is a lot stiffer than the 3.5. Otherwise, there isn't much more difference in terms of mechanics but the styling of the 140 is a little nicer, in my opinion. Also, the Bose radio is a weak spot, when it goes bad and you have to drive around without music in your 140, until you can figure out how to get some sound in the car. Also, I like to drive the 617, which once it gets going on the highway; it's just a Mercedes, just like the rest of them.

BenzDiesel