Hi,

I want to ask, as the previous S-Class 350SD/SDL W126 has been known for the nickname "rod bender" from the problems of , OM603.970, bending its connecting rod and ovaling its cylinders.

Does the OM603.971 of 300SD or S350 W140 still remain the nickname of the "rod bender" ?

And Is it true that the non-US or European model 300SD/S350-TD W140 hasn't face with the problem rod bending + egg-shaped cylinder ?

I found a great 1995 model year, Has it passed away from these problems yet ?

Thank you

Nobody knows ?

The E.U. versions suffered Possibly LESS failures.
M.B. 's Explanation dealt with the Poor fuel Quality available
in the U.S.
E.U. Cetane CAN be as high as 60
In America we're lucky to see Cetane of 40

Entertainment,Whilst I find G.M.'s article:

Rod Bender True Stories - How it Broke and Why

George Murphy's treatise VIA Maxbumpo on MBCA's website (Dated 2008) :

http://www.mbca.org/forum/350sd-sdl-and-s350-engine-problems

Text of Which is Below:

GeorgeMurphy;120584 wrote:

From my files - some a little dated:
At a recent Tech Session I had a chance to speak with Tom
Ischler, who is a TechRep for MBUSA. I asked him to speak with me not as a
representative of MBUSA, but as one car guy to another. I asked
point-blank: What is MB's position on the longevity (or lack thereof) on
the 603 engines.

His responses were rather illuminating. He indicated that the "bent rod"
syndrome and the premature cylinder wear problem were actually the same
problem at different times in the life of the engine. I won't do justice to
his explanation of the issue, but he broadly stated what MB believes to be
happening is that the 603 experiences severe detonation due to the lower
cetane fuels used in North America. In Europe, 60 cetane is not uncommon.
In US markets, 50 cetane is very rare, and low-40's is common. This leads
to detonation (pinging, were it a gas engine) after the piston has passed
TDC in the ignition cycle.

This detonation leads to the bent rods that many 603 owners have noted. The
rods, once bent, subtly change the angle of the piston and this is what
leads to the "egg-shaped" cylinder syndrome where the oil consumption
increase becomes noticeable.

What's interesting is that a compression test (hot or cold) will not
absolutely indicate a problem bent rod; compression may still be within
acceptable limits in spite of impending or existing internal damage. As a
semi-static test, the compression is within spec even though the rods have
begun to collapse. A compression leakdown test is flawed for the same
reason; it is typically conducted at TDC when the piston is beyond the
cylinder deformation.

The reason that MB pulls the head as a diagnostic action when 603 problems
arise is to determine if the problem is related to unsatisfactory
maintenance (i.e.: scoring of the cylinder walls due to poor maintenance).
Of course, once opened up the cylinders can be measured to determine if the
"egg-shaped" syndrome has commenced.

Anecdotally, he mentioned that placing a known-good rod next to a "bent" one
does not reveal an obvious problem. The bending does not appear as a
flexing of the rod, but it can be measured.

Finally, I pointed out to Tom that I had never known a 603 owner who did not
experience the oil consumption problem within the first 100K or so and that
MB seemed to be very evasive about owning up to the design flaws. He stated
that the policy was that owners complaining of 603 oil consumption problems
were handled on a "case basis" (taking into account the maintenance history,
owner history, etc...). There is, apparently, an MB form (that all Zone
Reps have access to) that must be sent to MBAG to approve an MB-covered
engine replacement. Tom stated that he had never heard of a request for
replacement that had gone all the way to MBAG that was denied. He also
stated that at 800/FOR-MERC, processes had been put in place to handle
complaints related to the 603 engine.

From official Mercedes sources, this is what we know: In October 1990,
shortly after this motor (the 603.970) went into production, MB revised the
configuration of the head bolts in order to strengthen the entire assembly.
When the 1992 version (the 603.971) went into production, changes were made to
the head gasket. Clearly MB was concerned about the ability of the head and
gasket to withstand the greater stresses caused by the increase in
displacement. Of course, essential to the motor's viability are the capacity
and integrity of the cooling and lubricating subsystems.

In search of the best explanation for our problem I have combed through the
archives of the various on-line discussion groups of the MBCA and several
other groups. I have obtained and searched through the AllData CD-Rom
containing the Technical Service Bulletins (TSBs) for my particular model
year. One of our members has shared with me an 'unofficial' acknowledgment
and explanation given to him by an MB Tech Rep.

The most specific material that I have received so far comes to me from a
concerned member. It consists of a service advisory (I'm not sure of the
precise title) contained on microfiche. It appears under a group captioned
"Removal and Installation of Engine, Crankcase (block), Cylinder Head,
Crankcase Ventilation." It is numbered 01-93101 and captioned "Engine Smokes
Blue, Makes Knocking Noises, Runs Unevenly, Valve tappets are noisy with
engine at operating temperature." It relates to engines 602.96, 603.96, and
603.971 (produced up to April 1, 1994). This particular bulletin was revised
October 1996. It describes the cause of these problems as "Insufficient
sealing of cylinder head gasket in area of cylinder head lateral oil channel
near cylinder no. 1" and describes the remedy as "Inspect combustion chamber
to determine repair, using boroscope if necessary, and replace cylinder head
gasket." It cautions that prior to re-installing the cylinder head, there
should be a careful inspection of the cylinder head lateral oil channel, the
removal of any burrs, and the lightly camfering (sp?) of the edges from the
lateral oil channel to prevent splitting of the head gasket sealing edge.

Soon thereafter, in December 1995, with a revision dated February 1996, a
"Service Tip" was issued, numbered 03T95121, captioned "Limited Availability
of Optimized Pistons" for Model 140.134 with engines up to serial number
603.971-12-018446. (I suspect that there were none manufactured thereafter;
these were probably sufficient for the balance of the 1994 model year, and the
very few distributed as 1995 models.) The service tip advises that "A very
limited availability exists of optimized pistons with piston rings for use as
remedy against oil consumption complaints." The tip directs the mechanic to
"verify related engine components are in correct working order and engine
control systems are functioning correctly prior to ordering or installing
these special pistons; verify no abnormalities or wear patterns exist with
cylinder bores; ensure cylinder bore honing is visible and normal." It goes
on to recommend reference to certain specific literature and work
instructions, but I do not yet have them.

I have also reviewed a Technical Service Bulletin, dated August 1994, that
advises of the availability of cylinder sleeves in the event one of these
engines is rebuilt.

These bulletins speak volumes about our problem. They confirm the legitimacy
of our complaints - excess oil consumption, mechanical noise, smoke, uneven
running. They demonstrate that enough of these problems had been brought to
MB's attention, relatively soon after introduction, that engines had been torn
down, specific problems had been found, and solutions (albeit partial) had
been proposed. They identify a likely cause - defects in or obstruction of
the lateral oil channel. The admonition that cylinders be closely inspected
is particularly significant, since it confirms what several of our members
have experienced - cylinders that have become out-of-round.

Since my last mailing, one of our members, Randy (aka "Cookies"), has
provided me with some more specific information on the type of compression
test that should be done on these engines if accurate readings are to be
obtained. He advises that the test should be done on a warm engine, and that
all injectors should be removed before the test begins. (Apparently some
mechanics remove the injectors one at a time, test that cylinder, and then
move on to the next one.) The test should be done with a MotoMeter
compression tool specific for diesel engines, p/n 001-589-78-21-00.
Greetings once again:

My apologies for being slow to get back to several of you, but a bad case of
the flu, too much work, and the holidays have cramped my style.

When last I wrote I advised that I was compiling a list of folks who have
encountered difficulties with this engine. Several additional names have
surfaced. The list now includess the following:

John Blazer
Dale Lockwood
Angelo Giaimo
Steve Sims
Vijay Kumar
Jackie Manson
Walt Lasher
George Hayos
Randy Leiser
Dan Rajaratnam
Albert Fellers (new)
Bob Mahoney (new)

Once again, some of these individuals have gotten relief from MBNA; some no
longer own the cars; some have paid for their own repairs; others are still
trying to get satisfaction. Please provide me with the names of anyone else,
not presently on the list, who have experienced a problem with this engine. I
will be sending a separate message to those on this list, requesting certain
specific information to aid in our investigation.

Since last I wrote I have found some data that is of interest, i.e. the
number of cars sold in the U.S. with this engine. The numbers are as follows:

1990 350SDL 855
1991 350SD/SDL 3,914
1992 300SD 1,131
1993 300SD 1,005
1994 S350 672
1995 S350 425

Finally, I note that for several of you I have multiple addresses. Please
advise if one should be deleted.

As always, if anyone from the MBCA list at large would like to receive
further communiques about this issue, please let me know.

Thank you for your continued interest and cooperation.

John A. Blazer
JABlazer@aol.com
MBCA-GWS
1991 350SD

Gary Hurst recently pointed out that there exists a website for dialogue about
the problems with this engine. Although I have been building my own data
base, and compiling data, this was the first that I had heard that such a site
existed. I browsed to it, and lo and behold, the page begins with my first
memo!! Not sure who created the site, but I am grateful. I will add to it,
and future references will most likely be to the site as it evolves, rather
than sending long e-mail messages to the various lists.

__________________
'84 300SD sold
124.128