S-Class (W140) 1991-1999: 300 SD, S 350TD, 300 SE 2.8, S280, 300 SE 3.2, 300 SEL 3.2, S320, S320L, 400 SE, S420, 400 SEL, S420L, 500 SE, S500, 500 SEL, S500L, 600 SE, S600, 600 SEL, S600L, 500 SEC, 600 SEC

1991 350SD... inquiry

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Old May 27, 2008 | 07:38 PM
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1991 350SD... inquiry

An opportunity has arisen to purchase a 91 350SD for about 9000 dollars US. Car has about 120k miles.

I am recalling discussion of Major Problems with the big Mercedes turbodiesels from about this era... or am I mistaken.

Any opinions would be welcome. I am not particularly handy but know some MB people who I would trust to work on it as things arise... but the car is at some distance and I cannot check it out myself.

Thanks for any help you can provide.
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Old May 27, 2008 | 07:48 PM
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From: New Zealand
1993 300SEL/S320
My understanding is that the 350 is a vary bad engine and bends rods. However there are a few that seem to run well into the high miles. IMO you're better off gettting a newer 300SD rather than the 350.
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Old May 27, 2008 | 09:31 PM
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The 1990-1995 350SD(L) / 300SD / S350 all have the same 3.5L "rod-bender"

If the engine was replaced with a factory replacement it will last forever, if rebuilt properly, it also should last.

I would reccomend buying these cars only with a documented replacement/rebuild, or buy one with a dead engine and pay for a crate engine/rebuild yourself.
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Old May 29, 2008 | 09:44 AM
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thank you

Another question: I was told by someone that not *all* of these engines were "bad". That in fact, if it has gone 200k miles on the original engine, that is proof that the engine is OK. Any thoughts?

The argument was that these engines (if they went sour) went sour after 70-80k miles.
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Old May 30, 2008 | 07:21 AM
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Originally Posted by jimsaco
Another question: I was told by someone that not *all* of these engines were "bad". That in fact, if it has gone 200k miles on the original engine, that is proof that the engine is OK. Any thoughts?

The argument was that these engines (if they went sour) went sour after 70-80k miles.

My understanding was that the rods were simply too weak, and that the amount of time the engine could be driven before failure was determined by the use of the engine and how it was cared for. If a car was running on synthetic oil and only on the highway, it may run for a long time even with the faulty rods, since there is very little load on or friction in the engine.

The bottom line is that anyone considering one of these (otherwise fantastic) models should do so with the intention of buying a new engine, if it has not already been done. I would personally like to find a 350SDL and put a new engine and a 2.46 LSD rear end (from a 560) for one amazing highway cruiser.
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