Your story highlights the beauty of the mystery with the problems on that 3.4L engine. Your car currently has 172K miles and still runs well. Well guess what? I own a car with the exact same engine as yours with nearly the same amount of miles and its engine has gone to hell. All oil changes were done between 2-3K miles. The owner was very particular about this. What gives? Well, no one knows and I don't think anyone will ever know.

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

The saga has ended for my friend who owned the 1991 350 SD with 182,000 miles on it. I really want ti thank al of you who gave me such excellent info and advice. Before my friend had a chance to act on any of it, the Lord took care of the problem for him: The car was totaled. My friend was rear-ended in traffic and got rammed into another car in front on him. The insurance check was very generous, good enough for the down payment on--I'm almost afraid to say it in this forum--a used Honda Pilot...

I do read a lot of problems about the 603 engine (3.0) and (3.5), the only thing I can report is; my wifes car 300td '87 have >700.000 miles on it, same engine, and my car '87 300sdl have now more than 723.000 on it, without any problems!! also same engine!!, but some blow-bay is showing now!, but!! the 603 350 (rebuild) is ready to take over!

Ohh, I.m a MB Tech for more than 40 years!, and also trained in the M B schools in the USA, before that, I.m worked in Holland, (born Dutch), as a MB tech in dealership,

I'll bet that Honda Pilot is junk and worthless now.

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Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)

I wasn't born Dutch, but my grandfather was!

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Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)

Welcome to the forum.

Great to have knowledgeable experienced members with the hands on experience.

Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Sorry to keep digging up this thread... but I just had a thought.

Let's assume that the reason the 3.5l engines bend rods is due to carbon buildup on the pistons / cylinder head, and repeated smashing of said carbon. The carbon comes from the EGR mixing with oily vapors from the CCV and turbo seals. Now why do the 3.0 engines not have this problem, even though they have EGR, CCVs, and turbo seals? Perhaps their EGR system isn't as aggressive as the one on the 3.5.

I know the 87 cars at least required a catalyst system to meet federal emissions. The 350s, as fitted to the W126 at least, do not need a cat. Perhaps they were able to squeak by with an increase in EGR?

A study of how much / often the computer activates the switchover valve for the EGR might yield more information.

FWIW I don't buy the dead glow plugs theory. The amount of fuel injected is so small, and many, many other diesels will start and run without damage when the preglow system isn't working properly. Plus most of the unburnt fuel would just be expelled on the exhaust stroke.

Another theory I heard was that crappy US fuel was igniting later causing cylinder pressures to be too high. Injection already starts at 15* ATDC, right? If the ignition happened later cylinder pressures would already be lower. I'm not buying that theory either.

-Jason

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

I dissected my '91 for the head, no significant carbon buildup, about the same as my '87.

The difference in emissions is due to the angled-injection, afterglow, and I expect to a more aggressive IP cam to create a higher injection rate, both known to create less emissions. Beyond that is the lower max. RPM / high-idle speed of the .970, lower RPM on an IDI engine is lower emissions.

I don't buy the glowplug one, nor the cetane one, but I think that the gasket-failure causing hydrolock is feasible, as is simply inadequate rods for the higher angle, but one would expect that to be an earlier failure considering 100,000miles is roughly 200,000,000 cycles of that rod.

Many of the .970 cars have new heads, many more have new head gaskets, there might be a connection.

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Gone to the dark side

- Jeff