As my 87 300SDL has been very expensive to maintain recently, my eyes have strayed to a 91 350SD, and of course I have (in the past) devoured a lot of information about these 350s, oil leaks, rod geometry and materials, et al.

Years ago I drove the SD, and it was a dream to drive. The one I am thinking about has reached over 150,000 miles, and seems to have spent some of its life in Europe, sipping good German beer....I mean low sulfur diesel.

Money's tight, so I haven't called the seller yet, but should I ask if the records show that the rods were replaced, or is this relevant any more? Are all these cars doomed?

The 3.5L is just a flawed design full stop. Can they go high miles? Sure. Do you really want to roll the dice? Your call.

The '91's have a lot of proprietary parts to them (engine mounts are a good example) that are extremely expensive compared to the '86/87. Keep in mind it's basically the same car, but with a more expensive to maintain engine than the one you have.

Unless your car is a beater and the one you're looking at is a garage queen with perfect maintenance history and you can get it for a song, I'd expect it to be a lateral move, not an upgrade.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Thanks for the response.

Yes my 300SDL has become too expensive, and I don't want to throw money at it.

My other idea...although I hate to give up all that sheet metal...is a 2005 E320cdi.

So you don't agree with those true believers that think that stronger rods will fully compensate for the different stroke geometry induced by the bored out cylinder? I suppose MB was crazy not to just start with a new block.

The 3.5L block lacks cylinder liners and the oil cooling jets (and oil cooled pistons) of the 3.0L. It uses the same head design as the 3.0L as well so the head gasket design is more highly stressed. They got the head right, but the block all wrong. Rods are one thing, but it's always going to be a half-assed design.

If maintenance costs are a concern, driving a 25-30 year old car probably isn't a good idea either. As they age, their cost to maintain will only rise as more things wear out and parts become more expensive.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

The 350SD makes a great platform to swap om606 turbo into. SD luxury + 606 power and reliability = best of both worlds.

Although if money is tight, taking on any new old car project probably isn't a wise choice.

__________________
1998 E300 turbodiesel

America's Rights and Freedoms Are Not The Enemy!

That is the best explanation I've heard for the engine failure. The whole thing about liners and cooling jets is completely new to me.

As you say the rods are also a factor, but with the points you made the 350 is a perfect storm of crazed design choices.

As I said, I like big cars, but the 320cdi looks better to me in terms of reliability. Do you have any opinion on the 2005-2006 models? I like the 350 body style from that era better. The E320 body is neither here no there, with a funky rear design that looks truncated to me style-wise.

Thanks. Those are great suggestions, but given the seller wants more than 8 K, transplanting my 3.0 L into it would be expensive. I am not a mechanoc.

And even them, costs would add p[ repair-wise, again making the E320 more attractive, but probably not as safe.

While your SDL is a very safe car for its time, I don’t think there’s any way it would be considered safer than the E320. The w211 has a ton of safety features the w126 does not.

That said, while I have never owned a w126, I’ve owned a w123 for 20+ years and a 2006 E350 gasser wagon since ‘08 that I bought CPO. While many folks here seem happy with their 05/06 CDIs, I have not found the w211 to be an inexpensive vehicle to maintain.

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Christopher
'06 Mercedes E350 station wagon (silver/black)
'85 Mercedes 300D (black pearl/palomino)
'85 Mercedes 300SD (smoke silver/burgundy)
'79 Cadillac Sedan DeVille

'05 Toyota Camry (because always running is nice)

'85 Mercedes 300D sold back to orig. owner 8-1-06
'84 Volvo 264GL Diesel, owned 2000-2013

You touch on a good point. German cars by and large are NOT cheap to maintain. They require a decent amount of attention and routine maintenance to hold together and go for the long haul. If ignored or maintenance is skimped or "deferred", you can expect big bills sooner rather than later. Some of the newer models (Bluetecs for example) require dealer servicing for something as minor as air filter replacement. Cram enough electronic crap and "dealer only" maintenance items in there and that luxury car quickly becomes a money pit.

Cheap to maintain = Japanese. That's pretty well the long and short of it. Keep coolant and oil in them and they'll go 200K pretty easily without much fuss. All the driving excitement of a bucket of warm wallpaper paste, but they're dependable.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Not wrenching and low on funds are the key prohibiting factors. I can't imagine owning any of these old cars if paying shop labor.

Let's change the discussion to what's wrong with your current car. With good fortune, they may be relatively minor things that this site can walk you through.

__________________
85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

Do you have evidence of this?
Granted I've never seen a 603.97x in my life, but I believe this to be incorrect...
Why would MB not bother if all their other 60x family have both (NA engines included from what I've read)

FWIW OP, if the SDL engine does have the factory rebuild tag on it, there'd be no difference in reliability from a normal 603 I would think.

__________________
1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD

the 603.970 does not have liners when new. There are repair versions available but they do not originally have them.

I guess the larger bore was a reason for that.

But why drop the piston oil jets... I'm sure I read even the NA 60x engines have them, makes zero sense that MB would leave them off a turbo engine. Can only think something like larger crank throws causing interference? But then the 2.9 OM602 has them still doesn't it, same stroke...?

(sorry for the thread hijack OP)

__________________
1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD

For a first time in my life I have an exceptional, honest and fair MB mechanic close to me, so I thin repair costs for the E320cdi would be manageable. No Japanese diesel car exists, and I like Benz mechanics.

The 300SDL has been through a lot, and throwing more money after a big outlay for suspension problems seems a dopy occupation.

Any owner on the thread who can share their opinion of the 2005-2006 E320 cdi?

There was a thread posted on this forum sometime within the last year that had a link to a PDF publication from MB themselves discussing the differences between the 603.96x and 603.97x and the subsequent 602 redesign that followed the 603.97x and the deletion of the oil sprayers and annular oil ring was one of the key design changes. If I can find the thread or the link I'll post it unless someone else has it handy and beats me to it.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)