Diesel Flywheel Issue - Do I Need to Replace?

[MSCH]

Well for my six cylinder engine I think I can see four specific spots where wear and engagement occurs. Each one is different than the next. I assume this means one is more frequent than the others.

having worked on diesel engines and knowing I had a choice of jacking over the engine using a bar or bumping the starter motor, I'd bump the starter motor to get it to the right spot. they dont automatically move, fact is most of them shut down immediately, quicker than a gasoline engine ,,, that said I have never marked an engine externally and actually checked..

at any given point depending on number of cylinders how many are on a power stroke and how many are on compression?
what about external factors like driven members..

anyway, you have a choice on the flywheel of waiting until it won't work any more, or possibly getting in there with a dremel and cleaning it up, or letting someone fix it.

 

[IndyIan]

I guess I need to understand better how these “bendix type” starter gears work. If the sequence is to start spinning which forces the gear forward, or to force the gear forward then spin.

I just don’t really get how such a slight engagement coukd be a thing unless it was the starter… or enough deformation of some teeth on the flywheel that they csnt mesh, and if the starter hits those it just grinds them off?

Maybe someone makes a non-bendix starter that would fit? Seems like this design wouldn't have this problem?

 

[JHZR2]

Maybe someone makes a non-bendix starter that would fit? Seems like this design wouldn't have this problem?

That design still has a design that meshes the pinion and flywheel. What’s the difference?

 

[IndyIan]

That design still has a design that meshes the pinion and flywheel. What’s the difference?

Bendix drive - Wikipedia

en.wikipedia.org

A bendix does spin up the starter motor first, to move the starter gear into the fly wheel, is what I gather.
To me it seems youtube video design should never run the starter with the starter gear half engaged, but the bendix one can shred gears all day.

 

[meep]

The first thing I would do is play with pulling the gear forward by hand. Does it go further? Does it catch and get stuck? Does it feel really loose? Should the solenoid be dismantled and looked at?

 

[supton]

Well for my six cylinder engine I think I can see four specific spots where wear and engagement occurs. Each one is different than the next. I assume this means one is more frequent than the others.

All have the same compression? wondering if 2 are down.

 

[Trav]

Strangely, I have three spots where there is wear.

I’d suspect it has something to do with the compression stroke of the strongest cylinders?



What do you mean by dressing the flywheel teeth?

I was thinking to maybe take a small file, smooth any asperities, and then either use a wire flux welder or JB weld (what’s the worst that can happen?) to fill in the flywheel teeth and then refile.

I suspect that rough imperfect “fixed” flywheel teeth may be worse news for meshing in the starter, but it beats the alternative. It’s also why something like jb weld would seem like a better bet if it would actually “grip”, since it could be shaped easier upfront and after. Maybe even with some sort of mold.

The only reason I can think of for having 3 sections of damaged teeth is a 4 cyl engine will stop in one of 2 places a 6 cyl in one of 3, pistons go up and down in pairs. I can only guess the original starter had some issue that prevented it for engaging the teeth quickly enough or was weak. Bottom line is to replace the flex plate.

 

[KrisZ]

The only reason I can think of for having 3 sections of damaged teeth is a 4 cyl engine will stop in one of 2 places a 6 cyl in one of 3, pistons go up and down in pairs. I can only guess the original starter had some issue that prevented it for engaging the teeth quickly enough or was weak. Bottom line is to replace the flex plate.

Precisely, there is no point trying to root cause this as all it takes is one or two weak engagements, for whatever reason, a weak starter, a weak battery. I've personally experienced starters that would start clicking or grinding after prolonged cranking during a cold start and it was because the battery was getting weak.
Then the teeth can get nicked a little and it just propagates from there.

 

[JHZR2]

The only reason I can think of for having 3 sections of damaged teeth is a 4 cyl engine will stop in one of 2 places a 6 cyl in one of 3, pistons go up and down in pairs. I can only guess the original starter had some issue that prevented it for engaging the teeth quickly enough or was weak. Bottom line is to replace the flex plate.

The car had a headgasket sometime back. This is beyond common in the 3.5L version of the OM603. I have to wonder if maybe a cylinder hydrolocked? Totally a speculation. Not sure if it would happen.

It seems that it either doesnt land there much, or it doesnt happen all the time.

Thing is, who knows if its the current (Bosch rebuilt) starter, or an older one.

Battery seems perfectly strong, and after the failed starts, it starts strong and perfect...

Any idea how many hours would be involved? Can this be done on my back?

 

[JHZR2]

All have the same compression? wondering if 2 are down.

Havent tested. Have no desire to test it, the engine starts and runs so well...

 

[JHZR2]

Bendix drive - Wikipedia

en.wikipedia.org

A bendix does spin up the starter motor first, to move the starter gear into the fly wheel, is what I gather.
To me it seems youtube video design should never run the starter with the starter gear half engaged, but the bendix one can shred gears all day.

So, the wiki says that the bendix design has been superceded by the solenoid design. Mine has a solenoid. So I assume it isnt a Bendix. I had been using the Bendix term, quite possibly totally incorrectly... and generically...

 

[Oro_O]

Did you figure out how far the starter teeth are supposed to engage? Full length (e.g.,, cover the entire surface of the flexplate teeth), or less?

 

[Trav]

The car had a headgasket sometime back. This is beyond common in the 3.5L version of the OM603. I have to wonder if maybe a cylinder hydrolocked? Totally a speculation. Not sure if it would happen.

It seems that it either doesnt land there much, or it doesnt happen all the time.

Thing is, who knows if its the current (Bosch rebuilt) starter, or an older one.

Battery seems perfectly strong, and after the failed starts, it starts strong and perfect...

Any idea how many hours would be involved? Can this be done on my back?

If you can get it high enough you can do this on your back, it is not fun but can be done. You need to pull the exhaust system, drive shaft and rear transmission mount cross member. Use a plug on the tail shaft to prevent it leaking all over the place.

There is more than one way to skin this cat, if you just want to replace the flex plate, support the engine, remove the TC and transmission to engine bolts, any cables and wires and put a transmission adapter on a floor jack, pull it back carefully and lower it but leave it under the car. replace the rear main seal if wet and flex plate and put it back in.

Figure on 8-9 hours if you never did one.

 

[Astro14]

I would do the rear main seal regardless. You’re there, it’s old, it adds fifteen minutes to a six hour job.

 

[Trav]

You are correct, I would also along with the front trans and tail shaft seal but there is a catch with the engine seal, this one is pre cassette style and requires a bit of tweaking if there is any wear on the crank end.

 

[JHZR2]

I would do the rear main seal regardless. You’re there, it’s old, it adds fifteen minutes to a six hour job.

For sure. The thing with this always becomes, if I’m doing all this work what else should be done. My angle is if I’m removing the AT then does it drive to the question of if I put in a rebuilt at, just because, or a torque converter, seals, etc.

 

[Trav]

The way I see it is, if it shifts properly and has no issues I would not swap it out. I mean if you remove it to do flex plate or rear seal it is not usual to replace the transmission just because it is out. Ditto rebuilding a good functioning manual transmission because you do a clutch job.
If you say change the seals and the transmission mount then sure makes sense to me, in the end it is up to you. I would keep in mind that rebuilds can be a mixed bag depending on who did the rebuilding.

 

[JHZR2]

The way I see it is, if it shifts properly and has no issues I would not swap it out. I mean if you remove it to do flex plate or rear seal it is not usual to replace the transmission just because it is out. Ditto rebuilding a good functioning manual transmission because you do a clutch job.
If you say change the seals and the transmission mount then sure makes sense to me, in the end it is up to you. I would keep in mind that rebuilds can be a mixed bag depending on who did the rebuilding.

That’s sensible. My angle was as much coming from my initial concept that I’d rather wait to replace the flywheel until I had to remove the AT for other more significant service. But what you say makes sense. And I should do the guibos anyway…

 

[wpod]

Btw you Asked why this happened. All engines stop in just 2 places regardless of where they were turned off. Nobody can explain why,

Depending on the number of cylinders the compression stops the pistons in the same spots .

 

[AITG]

When the starter is engaged the drive simultaneously extends and rotates so it will slide into the flywheel teeth. Over time a weak engagement will munch the flywheel teeth. On a two piece flywheel you can heat the ring gear until it expands enough to rotate it so the damaged teeth aren't at the engagement point but a flex plate may not give you that option. So, you can plan on pulling the trans or put up with turning the engine by hand to find clean teeth...up to you.

And yes, engines stop in the same spots. Always on the compression stroke. An inline 6 cylinder will have two places, 180 degrees apart based on 35+ years as a diesel mechanic .