All the S class models with the 3.5 liter engine, so both 126 and 140 models. I think the cut-off for the 3.0 liter engine in the 126 is 1987?

The root cause seems to be faulty head gaskets + weak connecting rods. The MB replacement engines have improved head gaskets and rods.

If a car doesn't have a documented replacement engine from MB, it will need a new head gasket and if you want complete insurance to make the engine as long-lived as possible, replace the connecting rods as well. Keep all documentation to prove this work has been done in the event you want to sell the car or the engine later on.

Another very reasonable "upgrade" is an OM606 turbo engine from a '98 or '99 E300 Diesel, but keep the OM603 3.5 liter injection pump and associated throttle linkage. OM606 has 24 valves and an intercooler, so a big jump in power compared to the OM603, and better fuel economy.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

I did a lot of thinking about the issue of the Rod Bender along with some pretty smart fellows and believe the issue was more due to the block being compromised by the larger bore of the 3.5 version. The flexibility of the block would precipitate partial failure of the head gasket allowing in enough liquid until the rod is bent by a partial hydrolock.

it only takes a bit over a teaspoon of liquid in the combustion chamber to fill it and cause partial hydrolock.

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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.

My roommate has a 1991 W126 350SDL as a daily driver. The original 3.5 engine died and it was replaced with a 3.0 from a 1987 W124 300D, which was a good choice.

It has ASD and I just got done rebuilding the tandem power steering pump. Keep in mind that rebuilt tandem pumps are VERY expensive, and I don't think you could buy a rebuild kit if you tried. My roommate and I scoured the internet for a long time and everyone that said they had a kit ended up coming back saying that they are no longer available. We finally found a place that had two older stock kits left and bought them both.

This one came stock with a parallel-flow condenser (it actually has a part number in EPC). Overall, it's a nice car, but it has a few parts that are impossible or expensive to buy new, and the same goes for finding the parts used.

For example, the plastic coolant reservoir is special to the 350SDL as it's skinny and long. Expensive. The radiator is specific to the 350SDL and it's not available new ANYWHERE for any price. So, you have to repair the old one, install a used one, or have one fabricated.

If you buy one, be prepared to replace the block or entire engine if it suddenly fails. Also make sure to have extra money on hand for those 350SDL-specific parts as they can be pricey. The transmissions are also prone to losing reverse due to having springs that are too heavy in the reverse clutch pack. All that aside, it's probably one of the best W126s made, and will likely be the most valuable model due to the low production numbers and remaining survivors, not to mention they sip fuel unlike the big V8 models.

Attached Thumbnails

 

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Stop paying for animal enslavement, cruelty, and slaughter. Save your health and the planet. Go vegan! I did 18 years ago. https://challenge22.com/

DON'T MESS WITH MY MERCEDES!


1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles

Are you sure? I’ve only seen ARV in ‘87s and ‘86s with a trap oxidizer. I hear not all ‘86s had a trap oxidizer. There’s no trap from ‘90 so they shouldn’t have ARV either. 140 SDs don’t have ARV. Certainly my ‘93 SD didn’t have ARV.

Are you sure also about boost control? IIRC 90-91/.970 don’t have a MAP sensor so they can’t have vacuum boost control.

Sixto
98 E320s sedan and wagon

Not 100% on any of it, information seems to be hard to come by due to the low production volume. I don't own a 350 and don't plan to. I can confirm that '86's came without the ARV and trap oxidizer, mine's one of them, and a late production '86 at that. Not sure what the big differences are between '86 and '87, but the '87's seem to be more common despite lower production numbers. Weird...

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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!)

I've owned a 1990 350SDL for 18 yrs. It just rolled 200,000. I bought it with 95,000 miles. Factory rebuild @ 75,000. The car is magnificent.
My only failure was a crack in the power steering pump mounting.

An all aluminum radiator specific to the 126 350SDL is readily available for $272. The overflow tank is $190.

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1990 350 SDL
Currently: 180,000 miles
Factory rebuilt bottom end rods, bearings and head gasket @ 75,000 in 1997

Where are you finding the radiators for sale? It will be the first time I've ever seen one available. $190 isn't too bad for a coolant reservoir. I've seen them at well over $200 before. Even over $100 used.

__________________
Stop paying for animal enslavement, cruelty, and slaughter. Save your health and the planet. Go vegan! I did 18 years ago. https://challenge22.com/

DON'T MESS WITH MY MERCEDES!


1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles

https://www.radiatorexpress.com/product.asp?part=1990+MERCEDES-BENZ+350SDL++-+3%2E4+liter+L6+RADIATOR+ALL+ALUMINUM+2+ROW&part_id=40225&aaia_id=1194476

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1990 350 SDL
Currently: 180,000 miles
Factory rebuilt bottom end rods, bearings and head gasket @ 75,000 in 1997

https://www.*********.com/gbproducts/WC/6243-01034899.html?utm_content=YN&utm_term=1990-1991+Mercedes+350SDL+Expansion+Tank+Genuine+90-91+Mercedes+Expansion+Tank&utm_source=google&utm_medium=ff&utm_campaign=*********+Google+Base&gclid=EAIaIQobChMIx8vf3pGF2AIVSEwNCh16tQwiEAQYASABEgLH_fD_BwE&ad=47433948732

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1990 350 SDL
Currently: 180,000 miles
Factory rebuilt bottom end rods, bearings and head gasket @ 75,000 in 1997

Oh, wow! Those must have just become available. Very custom-looking, but it seems like they are a direct bolt-on and without the awful plastic tanks. Thanks for sharing. My roommate's 350SDL has a large area that was filled with JB Weld and replacing the radiator would be a good idea.

There are lots of threads in the forum about people not being able to find radiators, so they've been using universal-fit ones and fabricating brackets.

__________________
Stop paying for animal enslavement, cruelty, and slaughter. Save your health and the planet. Go vegan! I did 18 years ago. https://challenge22.com/

DON'T MESS WITH MY MERCEDES!


1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles

I own a 350SDL, well hybrid, motor from 300SDL. My guess OEM failed as tech told me who had maintain this car for 15 years for the previous owner.
When I was replacing headlight/lights switch, so I found no bulb for ASD system in my cluster, since I removed cluster to replace this switch.
I put bulb and light will not go away. I guess it doesn't work or disconnected since motor from the 300 SDL - OM603.961. Look at my signature. But car pulls nice when it warm up.

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91' MB 350 SDL, with 961 engine and #14 valve head
09' ML320 Bluetec

this guys got two of them

https://newyork.craigslist.org/lgi/cto/d/1991-mercedes-benz-350sdl/6416095172.html

https://newyork.craigslist.org/lgi/cto/d/1991-mercedes-benz-350sd/6415768764.html

I can't seem to load the website for the expansion tank
www.*********.com $196.48

google 1990 Mercedes 350sdl expansion tank

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1990 350 SDL
Currently: 180,000 miles
Factory rebuilt bottom end rods, bearings and head gasket @ 75,000 in 1997

They look clapped out.

It's the "They run forever with no maintenance for 1 million miles!" guy again...

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

I don't want to hijack the thread, but i logged on tonight with the same question in mind, as i found this car in Houston.

https://houston.craigslist.org/cto/d/1991-mercedes-350sdl-turbo/6420105471.html

European Delivery Benz, Euro seats (no leather), looks like it is in mint condition. Trans rebuilt, but nothing on engine.

My dad wants to have a Bug out Benz, that he will drive very little, but can start up if an EMP goes off. he can either go all out and get this nice beauty or go ultra simple with a 240D manual (like me )

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Grey '91 350SDL 214k Dad's car
Beige '81 240D 4 Speed 254k SOLD
Blue '82 300D 225k SOLD
White '95 E300D 46k SOLD
Blue '87 190D 2.5 Turbo 315k SOLD
Brown '80 240D 4 Speed 716k SOLD
Beige '80 300D N/A 119k SOLD
Blue '85 300D Model 186k T-Boned