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Discussion Starter · #1 ·
I bought a 1985 300TD that had blown an engine rod around 2010. The owner bought what he says is a 300D engine that he claimed all I needed to do was switch the manifold and it should work. I'm an idiot for believing him, but although the car won't run, the body surprisingly has little to no rust. I bought the car with the blown engine/transmission and the 300D engine with its transmission. I also got a bunch of extra parts from the diner car along with an engine hoist and stand all for $1500.

My main question is will it work if I switch out the heads, I'm told the 300TD has the SLS pump in the head. And would the transmission for the 300td line up with the 300D engine? What else should I be considering?
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ForaBot's answer is created from summarizing the responses in this thread.

It is possible to convert a 300D motor for a 300TD, however it is not recommended. The 300D engine will need the head off the wagon OM617A to be put onto the sedan OM617A. Additionally, the transmission for the 300TD will not line up with the 300D engine, and the sump is different, so turbo drain is an issue. It is recommended to source a good Turbo engine and put the SLS head on it.
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1986/1990 W126
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I bought a 1985 300TD that had blown an engine rod around 2010. The owner bought what he says is a 300D engine that he claimed all I needed to do was switch the manifold and it should work. I'm an idiot for believing him, but although the car won't run, the body surprisingly has little to no rust. I bought the car with the blown engine/transmission and the 300D engine with its transmission. I also got a bunch of extra parts from the diner car along with an engine hoist and stand all for $1500.

My main question is will it work if I switch out the heads, I'm told the 300TD has the SLS pump in the head. And would the transmission for the 300td line up with the 300D engine? What else should I be considering?
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Can I recommend putting the car model a. D year into your profile for us please? Complete your Profile
 

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Discussion Starter · #5 ·
Yes, - You will need the head off the wagon OM617A to put onto the sedan OM617A - Have done this. Everything else is identical

Either that, or fit the 300D engine as is and use a W126 / W124 Power Steering / SLS combo pump to provide SLS
Would I need to be worried about compression? Someone mentioned that N/A compression 22:1, turbo is 21.5:1. I think I would also need to figure out the turbo oil drain.
 

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W123 300CD, W123 300TD, W202 C250D Turbo
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brrrhh - Looks cold in Minnesota at the moment.

That OM617 is the early version (non pencil glow plugs) - Can I get a front picture as it may well have the SLS head. I wouldn't use the donor transmission as it is the earlier 722.1xx and the rear cross member is different, if you can use the wagons trans, then I would (it will fit straight up).

If you have to use the wagon head, it will have larger valves (and sodium filled exhaust valves) but the casting is identical NA to Turbo. The CAM is different too, but they are interchangeable. So you can just fit the head. The compression is in the piston config.

Are you planning to put all the turbo peripherals on the NA OM617 ?

The sump is different, so turbo drain is an issue as you point out. Also the oil drain from the catchcan in the air cleaner goes into the sump. The Turbo IP has an oil line from the block to the unit (and your early OM617 probably has that). The injectors have a different pop pressure (but are the same). The non turbo OM617 doesn't squirt the underside of the pistons to lubricate / cool them.

Personally, I would source a good Turbo engine and put the SLS head on it. The wagon is worth it !
 

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Discussion Starter · #7 ·
Today felt pretty warm at 35 degrees haha. I think for now I will try to source a turbo motor but I鈥檝e had some difficulty finding one in the Midwest.
I think worst case scenario, I could switch the heads and just run the car without a turbo.
 

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You could also open up the original engine and see what "It's blown an engine rod" actually means .... Maybe it's spun a bearing and a crank grind with oversize bearings is all it needs .... (Wishful thinking I know)
 

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06'E350 wgn,05'E320 CDI,04'E320 wgn,85'300CD,67'230SL
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The cast iron anvil-like OM617A turbo engine (with the oil squirters to cool the pistons) is usually super durable with just routine oil/filter changes, and good for many 100's of thousands of miles. Unless it's run w/o oil, grossly overheated, or way overrevved; I'm curious how the prior managed to destroy it?

Anyhow....I agree with TSSharkey that it would be worth the effort to find a decent turbo motor. The 85's have a smoother-shifting transmission set-up so I'd stay with that IMHO. 85's, especially wagons, are the best of the best, so it could be worth considerable $$ if you keep it basically original.
 

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Discussion Starter · #11 ·
The cast iron anvil-like OM617A turbo engine (with the oil squirters to cool the pistons) is usually super durable with just routine oil/filter changes, and good for many 100's of thousands of miles. Unless it's run w/o oil, grossly overheated, or way overrevved; I'm curious how the prior managed to destroy it? Anyhow....I agree with TSSharkey that it would be worth the effort to find a decent turbo motor. The 85's have a smoother-shifting transmission set-up so I'd stay with that IMHO. 85's, especially wagons, are the best of the best, so it could be worth considerable $$ if you keep it basically original.
He said he was basically running it off of waste vegetable oil. He did a conversion but my guess is that had something to do with it.
 

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He said he was basically running it off of waste vegetable oil. He did a conversion but my guess is that had something to do with it.
Yikes, I have to wonder if he somehow hydro-locked the engine with water in the veggie fuel. I dunno if it's worth digging into the old motor. Did the rod go through the block?
What's the mileage on the car? Could be worth significant $$ fixed right.
 

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Discussion Starter · #13 ·
Yikes, I have to wonder if he somehow hydro-locked the engine with water in the veggie fuel. I dunno if it's worth digging into the old motor. Did the rod go through the block?
What's the mileage on the car? Could be worth significant $$ fixed right.
Yeah maybe, he also mentioned he had a mechanic look at it and said something about how it was soon to fail.
Yeah the rod shot out from the bottom. The mileage on the car is 198279. I bought it since the body was pretty good shape, however the seats could use some work. I figured this might be a good chance to own one without paying the crazy mark up.
 

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W123 300CD, W123 300TD, W202 C250D Turbo
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Yeah the rod shot out from the bottom.
These have two stage sumps and the rod may have gone through it meaning the block itself is OK ? And the crank ? It may be cheaper (and in keeping with matching numbers) to replace the pistons, rods and lower sump ....
 

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If it helps.....I checked with a salvage yard in North Carolina that specializes in Mercedes 123 and 126 diesel cars; and they do have a used turbo engine available if you're interested in a comparable cost option to repairing the turbo engine you have. Parts Depot 336-842-6550 ask for Scott and he could tell you more.

There's also a shop in Titusville FL that really knows these cars inside out. Owner Pierre Hedary has a You-tube channel with loads of informative info on maintenance and repair of these 70's-80's MB cars in particular.

Hope this helps in your journey. -Vinny
 

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.................... ~'84 300D~~~~~~~~ ~~'85 300TD~~~~~~~ ~~~W123(s) Galore~~~
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I had an '83TD that had the SLS Removed (not by me) and replaced with New Heavier Coil Springs & Bilstein HD(s). While it road a little stiffer it handled MUCH BETTER than the '85TD with the SLS. That kit is around 350 including the Bilsteins. If my SLS ever goes out on the '85... I will do this conversion. The hydraulic shocks are around what these days... 500-600 each, accumulators 150 each, rebuild the SLS valve? Going this route would allow you to use your 300D engine as is.
 
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