wileycat · Feb 3, 2025

One of your American cousins has messed up and needs your help (No - we didn't invade any country. This is just an engine problem). I am running an early 1990s 200Tdi in an ex-MOD 110. I've run and loved this truck for 30+ years. Driving along on a remote overland trip and the Woodruff key that secured the harmonic damper sheared off. I kept driving it as it was still spinning the water pump and alternator (but with a helluva awful noise whenever I had to stop). Pulled it all apart and went to replace the damper as the inner tapered surface on the old one was chewed up. When the new damper was secured it does not run true but wobbles about 3 mm per revolution. Tried a second damper with same result. I have taken a bunch of measurements and finally concluded this -> I chewed enough off the tapered crankshaft extension that the damper now bears against the timing belt drive cog before becoming tight on the crank. The only thing I can see to do is pull the crank and either replace it (likely, given that Turner has a new one they recommend) or TIG weld a bunch of material on the old crank and re-grind it. Only other thought I have it so make a thin brass shim (a cylindrical thin shim) that I would then use to make up for the lost taper. Seems like a long-shot but might be worth trying before pulling out the engine to replace the crankshaft.
A second but related question -> The engine runs fine with about 130k on it. No smoke at all once warm and is a strong puller. If I have to swap the crank what else would you do while you have the engine out on a stand? Main bearings, con rod bearings, rings, piston pins? Timing belt and tensioner of course but what else?

lynall · Feb 3, 2025

I would bodge up whatever I could to save taking the crank out.
Maybe lightly take an angle grinder with a flap disc to the crank taper as the engine is ticking over? obviously not for to long as no water will be circulating.

wileycat · Feb 3, 2025

lynall said:
I would bodge up whatever I could to save taking the crank out.
Maybe lightly take an angle grinder with a flap disc to the crank taper as the engine is ticking over? obviously not for to long as no water will be circulating.

It is worth trying most anything. I hate to pull an otherwise good engine and tear it down for this problem. I found I can get coiled brass shim stock. I am thinking of running the engine and trying the grind approach, but need some info.

(1) To grind I have to keep the damper off and hope the Woodruff key keeps the timing belt cog in place (Or does it have its own separate key?) That's scary because if the cog flies off I wreck the engine.

(2) Realistically I will have to grind with the front of the timing case off in order to get to the part of the crank - that means the water pump is off and the coolant is drained. Maybe 30 seconds of run time before shut down.

(3) Does anybody know how far proud of the crankshaft end the harmonic damper should be on a unit that is not messed up?

lynall · Feb 3, 2025

wileycat said:
It is worth trying most anything. I hate to pull an otherwise good engine and tear it down for this problem. I found I can get coiled brass shim stock. I am thinking of running the engine and trying the grind approach, but need some info.

(1) To grind I have to keep the damper off and hope the Woodruff key keeps the timing belt cog in place (Or does it have its own separate key?) That's scary because if the cog flies off I wreck the engine.

(2) Realistically I will have to grind with the front of the timing case off in order to get to the part of the crank - that means the water pump is off and the coolant is drained. Maybe 30 seconds of run time before shut down.

(3) Does anybody know how far proud of the crankshaft end the harmonic damper should be on a unit that is not messed up?

I had in my mind it was just the damper itself, but if all that has to come off I would say new crank time, or crank rework time.

Item number 4, two of, so I would have to assume cam drive gear has its own separate key.

wileycat · Feb 3, 2025

That looks consistent with what I can see with the timing belt cog still in place. I have a new idea - I can pull off everything down to the timing cog and use a long belt of sand paper to encircle the rough part of the crankshaft extension and hand sand about 180 degrees of the diameter at a time, then manually turn the engine a few degrees at a time and keep repeating. That will give me a smooth surface - but likely not one that has the exactly correct taper any more. I then try the extrudable brass shim stock and see where I get.

Likely won't work but worth a try. In any event - I promise to report back and thank you for any and all input.

tottot · Feb 4, 2025

Pic above is of later crank with no taper. Some twenty years ago a mate had a similar issue on a 200 in his disco and asked for my help. He was a bit short at the time and asked If I was willing to have a go at a "bodge" repair.
The pully had spun on the taper, worse the woodruff key slot in the crank nose had a chunk out of it.
I rebuilt the slot with weld and ground it back to shape best I could. Cleaned up the mating surfaces of crank and pully.
Renewed cam belt [ we thought did not want to go in again] Think I spot welded each end of the key in place to prevent movement it still had. Covered i the lot in bearing lock and did the bolt up with thread lock good and tight.
Engine went on for years until rust finished the Disco. Last I heard a few years ago it was still in use in a 4x4 trials truck.
If you think rear of pully is in contact with cog would it be possible to remove some metal so it once again goes tight on the taper?

julianf · Feb 4, 2025

The damper isn't a mega precision item.

Personally I would try and modify the key (weld a bit onto the key) to suit the worn crank, rather than the other way around.

wileycat · Feb 4, 2025

tottot said:
Pic above is of later crank with no taper. Some twenty years ago a mate had a similar issue on a 200 in his disco and asked for my help. He was a bit short at the time and asked If I was willing to have a go at a "bodge" repair.
The pully had spun on the taper, worse the woodruff key slot in the crank nose had a chunk out of it.
I rebuilt the slot with weld and ground it back to shape best I could. Cleaned up the mating surfaces of crank and pully.
Renewed cam belt [ we thought did not want to go in again] Think I spot welded each end of the key in place to prevent movement it still had. Covered i the lot in bearing lock and did the bolt up with thread lock good and tight.
Engine went on for years until rust finished the Disco. Last I heard a few years ago it was still in use in a 4x4 trials truck.
If you think rear of pully is in contact with cog would it be possible to remove some metal so it once again goes tight on the taper?

Removing metal from the rear of the damper is a good idea. I have an old 3 axis mill that will do that nicely. I could then make a shim plate to move the pulley forward just a bit.

wileycat · Feb 4, 2025

julianf said:
The damper isn't a mega precision item.

Personally I would try and modify the key (weld a bit onto the key) to suit the worn crank, rather than the other way around.

The Woodruff key itself does not seem to be causing a problem. Do you mean weld material to the tapered inner bore of the damper? That could work. The trick there is that the damper has the inner part and the outer part with some kind of polymer in between. You'd have to go really slowly on adding material to not burn up the polymer.

These are all good suggestions - thanks

julianf · Feb 4, 2025

wileycat said:
The Woodruff key itself does not seem to be causing a problem. Do you mean weld material to the tapered inner bore of the damper? That could work. The trick there is that the damper has the inner part and the outer part with some kind of polymer in between. You'd have to go really slowly on adding material to not burn up the polymer.

These are all good suggestions - thanks

Apologies, I skim read. I had a 300 that chewed up the key on the crank sprocket, and my head was on that.

You can run a cold engine for a while without the water pump. On the 200 does the pump come off with the timing chest cover? Even if it does, which I wasn't aware it did, you could just clamp the hoses and fill the system with water. It will take some time to boil even without flow.

It is hard to understand how the crank would be ground off center with a stuck damper. You can easily see how the damper could be ground off center by the crank, but it's the crank doing the spinning.

I do feel like I'm not spending enough time reading the thread though, so maybe I should just shut up.

wileycat · Feb 4, 2025

No worries sir - all help is appreciated. The water pump does have to come off to remove the timing case front cover, but as you say the hoses can be clamped enough to fill the water jacket and run for a short while.

wileycat · Feb 4, 2025

Thought some pics might help - Here is a shot of the start of the problem. Woodruff key sheared off and allowed the damper to spin and chew on the crank

wileycat · Feb 4, 2025

Here is same shaft after it was cleared up and a replacement damper was installed. After noticing the wobble I used a puller to remove the new damper. This shot is after I removed the damper. There is still grease on the shaft from the installation. The key looks cocked up a bit but that was just from the removal. It seats well in the slot in the crank and it is a good press fit in the slot in the damper.

These pics were helpful to review. In looking at the first of the two pics (post before this one), there is a protrusion on the cog just to the left of the key position (approx 10:30 position to 12:00). It is this protrusion that is bearing against the back of the damper when I tighten the thing to required torque.

wileycat · Feb 4, 2025

And one more... This shows the first replacement damper I tried. If you look at the rear surface you will see a witness mark where that surface was bearing against the cog upon tightening. On this damper I thought the outer diameter was a bit large and that is why it is turned down (I turned it). It is also shown with the dust cover removed.

tottot · Feb 4, 2025

Yours is nowhere near as bad as the one I described in my post above, yours is the later type as in pic above [ early Disco 200 had a very steep taper on the end of the crank]
Looks well on the way to a fix. I would use a new crank bolt. Good luck.

dag019 · Feb 4, 2025

tottot said:
Pic above is of later crank with no taper. Some twenty years ago a mate had a similar issue on a 200 in his disco and asked for my help. He was a bit short at the time and asked If I was willing to have a go at a "bodge" repair.
The pully had spun on the taper, worse the woodruff key slot in the crank nose had a chunk out of it.
I rebuilt the slot with weld and ground it back to shape best I could. Cleaned up the mating surfaces of crank and pully.
Renewed cam belt [ we thought did not want to go in again] Think I spot welded each end of the key in place to prevent movement it still had. Covered i the lot in bearing lock and did the bolt up with thread lock good and tight.
Engine went on for years until rust finished the Disco. Last I heard a few years ago it was still in use in a 4x4 trials truck.
If you think rear of pully is in contact with cog would it be possible to remove some metal so it once again goes tight on the taper?

I did the same thing when the same happened to my crank, not as bad as the OP but I just cleaned it up as best as I could and then assembled everything with bearing lock to prevent it moving! Was still going strong 150k later and is the engine that is going to get rebuilt after the fire.

wileycat said:
And one more... This shows the first replacement damper I tried. If you look at the rear surface you will see a witness mark where that surface was bearing against the cog upon tightening. On this damper I thought the outer diameter was a bit large and that is why it is turned down (I turned it). It is also shown with the dust cover removed.

I may be wrong but is the damper not supposed to pull up against the pulley to clamp the pulley in place as well? otherwise what keeps the pulley from moving up and down the shaft? Looking at the parts diagram above it certainly suggests that. Is it not the woodruff keys that prevent it slipping on the shaft rotationally and the fact everything is clamped together by the bolt that prevents movement longitudinally?

Also shameless self promotion here, I currently have a reground crank out of an abandoned disco 200tdi rebuild that is for sale. I know you are across the pond but I am happy to ship if you do go down the replacement route.

wileycat · Feb 4, 2025

Uh oh - If it ain't the damper holding the cam belt cog in place then I don't know what else is. On the other hand - if you look at the first picture I posted the way the Woodruff key sheared kinda suggests a gap was there between the belt cog and the damper, but maybe that gap was part of what caused the failure.

As for the reground crank - If I have to get a replacement it will be coming from the UK anyway so that may be a great option and a good deal for both of us. Do you know how far under the journals are ground?

tottot · Feb 4, 2025

From what I understand it was some sort of protrusion on the cog that prevented pully sitting tight and square against it.

dag019 · Feb 5, 2025

wileycat said:
Uh oh - If it ain't the damper holding the cam belt cog in place then I don't know what else is. On the other hand - if you look at the first picture I posted the way the Woodruff key sheared kinda suggests a gap was there between the belt cog and the damper, but maybe that gap was part of what caused the failure.

As for the reground crank - If I have to get a replacement it will be coming from the UK anyway so that may be a great option and a good deal for both of us. Do you know how far under the journals are ground?

I can measure and check for you, and see if my friend remembers (I bought all of the parts left in his shed when he emigrated so I did not get it done myself), however, I probably have the shells for it in the box of engine rebuild parts so will check what size they are as well.

wileycat · Feb 12, 2025

Some work progress to report. After cleaning up the crankshaft extension (with the Woodruff key out) it really did not look too bad. I then set out to carefully measure it. From the cam belt cog all the way out to the end of the shaft it measures 1.241 +/- .002 (That's 31.52 mm). There is no taper and I do not think there ever was a taper on this one.
Then I measured the interior dimensions for the three new crank dampers I have. They measure 1.253 +/- .003 (That's 31.83 mm) all the way through. They have no taper either.
It looks like the crankshaft wore very evenly, but now I have a diameter that is way too small (.014 too small in diameter or .007 in radius). I have ordered some .007 brass shim stock and will attempt to use this to fill the gap.
It is tough to hold the shim stock in place while you feed the damper over it. I may need to use some epoxy to secure it. I may need to use some low temperature solder and solder it in place. I will report next when the .007 arrives.

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