I'm looking at a 91 350 SDL, which apparently has had no engine work done, including upgrades or modifications. Of course I've read everything on this thread, but I just spoke to a Mercedes mechanic whose theory was that this engine was more susceptible to carbon accumulation when driven in stop and go, and urban speeds. He didn't know about the stronger rods.

Putting that aside, was the 91 already modified by Mercedes, or are number of these still problematic. Wouldn't it be better to look for one whose engine had been modified?

Thanks,

Peter4

If you like it buy it, just remember that one day it could/might/possible/maybe bend a rod. I was told that 1995 was the best year of the 350's. A member on this forum has one that needs a new engine, overheating not bottom end related. When he replaces the rods with the updated rods I would be interested in seeing side by side pics.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Considering the prices people ask for these cars, they have got to be the poorest purchase anyone can make. The 3.5's are deceivingly reliable. They will never let you down. Even at -10 degrees, with good compression, they'll fire without a block heater as if it were 50. That is, until they start using oil like no tomorrow.
Progressive engine damage can occur over tens of thousands of miles from 2000 miles a qt consumed to 50 miles a qt. My 350, with the "new and improved" 3.5 liter engine has suffered the same fate. Either a cracked ring or a bent rod(severe loss of compression in #1), and given the history of these engines to me, it suggests the latter.

Meanwhile I'll just put around in my SDL, (I fixed the bumper cover), getting 28 mpg and burning 0 oil in 2500 - 3000 mile oil change intervals.

Oh, BTW. My 350 engine was replaced in July of 1995.

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1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)

Prices for these things are insane! I did an Autotrader.com search and people were asking $10k-$15k for cars with 200k+ on them. Mint 100k ones seem to fetch close to $20k! I'd rather buy a 560SEC they will hold their value better. I would never spend close to $20k on a W126 sedan, sorry thats E300D territory.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

So what is the matter with them? Why do people ask those ridiculous prices for a potential POS?

I am most befuddled.

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1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)

I guess they think they are worth something. People must be buying them, for a market to set prices you need buyers.

I wouldn't pass up a nice 350. I think a 1995 S350D would be a great car to have, a W140 with a 350 what a great combo!

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Why? Would you want to end up replacing the engine after 200K miles?
If I had to buy a W140(I wouldn't since it is the S-Class I least appreciate), I would go for the 300SE/S320. Relatively good fuel economy, and plenty of power thanks to gearing.

Consider, the 300SE/S320's are much more inexpensive than the 350's and the 350 in a 600 lb lighter car would blow the doors off a W140. And get better mileage.

Oh well, to each his own. I'm not going to dictate my opinions. I respectully disagree.

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1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)

Has anyone here actually done a side by side comparison of the 140 6 cyl diesel's and the 140 6 cyl gas? Purchase cost, Performance, Gas mileage, Maintenance, Reliability etc? Just curious which would win in the end comparing all the various factors. Even comparing the w126 1988 and newer 6cyl gas with the 300 & 350 SD & SDL's would be interesting.

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Mercedes Fleet:
2004 CL600 Designo Espresso SPORT
2004 S600 Designo Espresso SPORT/Lorinser Pkg.
1999 S320
1988 300TE
1972 280SEL 4.5
Diesel Fleet:
2014 GL350 Blutec
1987 300SDL Blk/Blk 4 place seating #18 head
1987 300SDL Smk Slv/Burgangy #17 head
1986 300SDL Blk Pearl/Palomino #14 head w/ 280K
1984 Lincoln Mark VII Fact BMW Turbo Diesel

Mine just turned 250,000 miles and I love the car. I had to replace the head gasket and valves recently but I consider these things regular maintenance at the miles I have on it. I used to be worried about the rod issue everyone speaks about but I have had no problem like that. I get 26 miles per gallon and the car is one sweet ride. It starts every day all winter and I live in Minnesota.

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91 350 SDL
91 300 E
85 300 D (sold)
79 300 CD (sold)
91 300 CE

1991 350SDL Engine Problem Prevention ,PETER GO TO SEARCH AND TYPE THIS IN AND YOU WILL FIND SOME EARLIER INFO ON THE 603 ENGINE
LARRY PERKINS
71 OLD DIESELS

i have a '90 350sdl which i bought for cheap enough to redo the engine if necessary. i have done a valve job and head gasket. the car still has a very noisy idle which may be a leaky turbo seal (any comments?). the car has oodles of power is smooth and the nicest to drive on the highway of any benzes i have had and ive had maybe 30. my 500sec drives pretty much as nice but with much less economy and a cramped back seat. i really llike the 350 and if i have to rebuild it i may change it to a 300. it has 140,000 miles, the interior is excellent, body very good .

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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.

If a 350 burns ANY oil less than 3,000 miles, I'd be skeptical. In my mind, they're all potential junk. New and old.

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1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)

See here... http://www.peachparts.com/shopforum/showpost.php?p=865322&postcount=19

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

The frustrating thing about these cars is the lack of agreement on their reliabilty. Based on the where there's smoke there's fire theory there would seem to be a real reliability issue with these cars. However, not only do Mercedes technicians deny that there's a problem, but so do a number of mechanics that work on these cars, to say nothing of sellers of these cars, private or otherwise.

Then, among the people that admit there's a problem, some say that if the rods are replaced or Mercedes did a rebuild or replacement that there's no problem. But others with the rebuild have experienced the meltdown.

Then of course you have those who have no problems!

I drove a 91 350SD, and really liked the feel of it, but I wouldn't take a chance on one with no rebuild, and one third of its records unavailable.

Peter4

I think the only ones to be taken as credible are those who have had specific longterm experience with them.

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1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)