About the vehicle:
-1984 Toyota Pickupwith om617 turbo diesel swapped in
-Mated to toyota 5spd trans with custom adapter plate from diesel swap company.
~120k miles on engine, with ~15k miles on swap
-Aquired about a year ago
-Cannot stress enuf how beautifully this engine ran prior to breakdown
(Cold starts down to -5 F unplugged!)

So short version of the story is....the crankshaft broke at the rear main seal after significant oil leaking from the seal. Most likely due to the mounting bolts for custom adapter plate that mates the 617 to the R151 transmission coming loose (or not being torqued in the first place?)

If yall want the long version of how this all came to pass and what all symptoms led to the breakdown then i can write it out but basically what I’m really wondering from anyone who has some insight is....

What considerations do I need to take into account if were to attempt to replace the crankshaft?
What damage could have happened that I’m not seeing looking into the bottom of the engine?
How can I check?
What absolutely needs replacing if I’m installing a new crank?

Engine is already out of the truck, on a stand, and upper oil pan is removed. I also have a donor turbo crankshaft ready to gothat I was hoping to swap in.

I’m not at all new to working on 617 engines but this is my first time staring down a rabbit hole of this magnitude, so any and all insight would be appreciated. Ill post a couple photos too.

(And Yes i realize that buying someone else’s diesel swap project was my first mistake)

Video of flywheel mount before i removed upper oil pan:
https://youtu.be/6LK7nz4FgtY

Video with oil pan removed, broken piece now unstuck.
https://youtu.be/bbCyO-vEqCA

Thoroughly clean and inspect the bearing cap, the bearing saddle in the block and the rear main seal contact area for cracks and/or damage.

Torque the main caps in place and measure for concentricity. If good, put the used crank in and I'd go as far as to say the used bearing inserts from the replacement crank IF they are excellent and kept in order. Plastigage everything looking closely for uneven sqwish. If it specs out good run it. Probably a good idea to use the main bolts from the donor motor if in good shape.

Saw a broken crank similar to what you described on a 616 IIRC at a friend's shop 3-4 months ago on a completely stock application; so it may not be your adapter that caused the problem.

Good luck and please post your progress.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

I would want a good machinist to look at the block for damage. I imagine the crank was partially broken when the oil started coming out then broke in a way that allowed it to come apart.

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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.

Absolutely confirm your flywheel is balanced properly and the bellhousing adapter is made right. One company that had (paste tense) a big name in the 617 swapping crowd made some pretty sketchy adapters, and a lot of people install these motors without proper match-balancing of the new flywheel to the old flex plate. The 617 is dynamic-balanced and the flexplate or flywheel is part of that, so said balance must be matched on whatever is bolted to the back of the engine in a swap.

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'82 300CD
"Pearl", the very first turbo diesel 123 coupe
Totaled 11/23/18, rebuild in progress.
'85 300TD, "Artemis".
'78 300D euro, "Ol' Red", mostly retired.
'85 300D, "Gandalf".

Balancing is a great suggestion,
I completely missed that!

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

SugarBear, that’s almost reassuring to hear you saw a similar broken crank on a stock w123...I’ve had lots of trouble finding any info on either complete rear main seal failure or broken cranks...can’t even find a good diy tutorial on removing the crankshaft!
The flywheel was reportedly sent out to a machine shop to be be redrilled and balanced by PO....don’t have a name on that shop, but should I have it redone just to be sure? Should I start with a fresh (used) flywheel?

CDTurbo, I just looked it up and my adapter is from the now defunct TDSwaps maker out of Oregon...is that the maker you were talking about?
Though from reading the drama on their FB page the adapter was purchased 6-7 years ago before the company changed hands and tanked...were the plates considered sketchy before that?
Right now my main concern with the adapter plate going forward is making sure the mounting hardware is properly torqued and threadlocked..but the quality of the machining looks fine to my totally untrained eyes and hands. I’ll have to do some more research on assessing the quality of the plate, but thanks for bringing that up!

I’ll be picking away at this over the next week or two. Thanks for any and all info and advice everyone, keep it coming!

Please share some pictures of the carnage .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

The crank and flywheel should be balanced as an assembly...pretty certain that is what CDTurbo001 is saying. If you have the crank balancer, crankshaft and flexplate from the donor motor I guess you could use the crank balancer, crank and have the flywheel balanced to match the donor flexplate;but, I'd be much more comfortable with balancing the donor crank balancer, crank and new flywheel as an assembly minus the clutch. I'd then have the clutch balanced if that's feasible by itself, that way future clutch replacement/balancing would be independent of the engine rotating parts.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

I redid the rear seal on Mutt the Race Truck's OM617 so I was in almost as far as you are to do that. A couple of tips learned.


1) Slightly offset the ends of the rope seal from the upper pan/block interface. This makes it pretty unlikely that the seal will leak at that interface.


2) Remove the upper spike in the seal channel. This makes should make it MUCH easier to install the seal and the lower spike (the one in the upper pan) is adequate stop the seal from rotating - in reality, millions of US engines were made with no spikes and spinning of the seal was not an issue. Further, this mod makes it possible to replace the seal in the future without lowering the crank as you can pull the seal like in an old US engine, for example a small block Chevy.


3) The anerobic sealant (as recommended in the manual) is available from Permatex so you don't have to spend the bix bux for the Mercedes stuff. I got mine at Advance Auto.


4) There are step-by-step pics in my build thread which might be worth looking up. Yours will actually be easier given that you have the crank out.



If I think of more I'll send them along.


Dan

OK got the broken crank out today, so here’s photos of all the damage I can see. I haven’t busted out dial calipers or plastigauge on anything yet but depending on what yall tell me about the pictured damage to the rear main seal contact area thats gonna make or break the rest of this project.

Photo 1&2 : break in the original crankshaft

Photo 3 : can see how flywheel stretch bolts pounded into the block and cracked outside of rear seal groove

Photo 4 : passenger side of upper rear main seal groove (in block)
Photo 5 : general top view of upper rear main seal groove, notice the warping from crack

Looks like getting a new rope seal to properly mount is out of the question in the current state of the block.
What do you guys think? My neighbor is very talented welder with a full shop...think if i tapped the seal groove back into place as best i can, he could fill the crack with weld and grind smooth?
Any other ideas besides getting a new block?

Full Disclosure: i have another 617 on a pallet i could drop in...but i kinda had something else in mind for it so if i can save this one I’d really prefer to do that....within reason of course....just so yall know that I’m not SOL if this block is toast.

Attached Thumbnails

         

Photo 6 : Driver side crack in upper rear seal groove
Photo 7 : first upper bearing halve back from the flywheel, showing lots of scoring and wear.

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The broken crank looks similar to what I saw at my friend's shop. Try torquing the bearing cap in place and check for concentricity. If it is good install the crank (mains only) and plastigage the mains looking for any uneven squish and clearance. Rotate the crank for any binding.

The scoring on the back of the main cap doesn't concern me if the plastigage looks good.

Since it is a rope seal the backside shouldn't matter a lot, weld it fit/rebuild the groove and put the seal in. If this was a neoprene seal the groove tolerance would be more critical.

Good 617's are getting tough to find and are expensive to rebuild.

Go for it and good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Bh:

Re: Pic #3
The bolt marks in the back face of the block were likely caused during the first mounting of the manual trans flywheel to the crankshaft. Odds are that the bolts from the autobox flywheel-flexplate stack were used; they are longer than the bolts for a manual trans flywheel. If the too-long bolts were driven in without regard to the feel of bottoming, they would produce the circumferential crack that is visible. The error would have been discovered when the engine could not be rotated.

It looks do able to me but I'd scrap it .

You didn't say where you're at, in the South West there are still plenty of good donor cars with solid engines being scrapped out .

Maybe try junkyard dog .com or whatever....

Should be some in the rust belt, maybe Rich has one he can palatalize and ship to you.....

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better