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Old 11-10-2019, 22:51   #1
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Yanmar 4JH2-TE Crankshaft Pulley has a groove

On a Yanmar JH2-TE, the crankshaft pulley has an extended core (don't know the correct engineering term) that fits over the end of the cranskhaft (see Crankshaft Pulley photo). The pulley is a press fit over the end of the crankshaft, and a large washer and bolt secures it in place. The outer surface of the pulley's extended core is precision machined, and mates with the front oil seal, which is located in the gear case cover. In other words, the seal that keeps the oil in the engine is not formed around the crankshaft itself, but around the crankshaft pulley. My engine was leaking oil there, so I pulled out the pulley to have a look. In the Crankshaft Pulley photo, you can see a groove about 1 mm deep. For a closeup, see the Crankshaft Pulley Shaft photo. I'm trying to decide if that groove is supposed to be there, or is the result of 2,700 engine hours of wear.

The Crankshaft Pulley and Seal photo shows the replacement seal (correct Yanmar part). In the picture, it is facing the way it would face when installed. The back side of it is facing the top of the photo. The back edge of the inner seal surface has a ridge, which I assume to be designed to fit snugly around the pulley core. But the ridge looks like it might have worn that groove in the pulley core.

So my question is this: do I need to replace the crankshaft pulley? Or is the groove supposed to be there? If the groove was caused by wear, I will definitely need a new pulley -- if I had the groove machined out, the core's diameter would be way too small to make a good fit with the seal.
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Old 12-10-2019, 05:16   #2
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Yanmar 4JH2-TE Crankshaft Pulley has a groove

It is not supposed to be there, the seal caused it, it’s wear. It’s common, often caused by old seals that get hard as they get old. It was almost certainly the cause of your leak.
You can deal with it a couple of ways, most of us will polish it out with crocus cloth, real fine sandpaper, cut it in 1” wide strips and polish it like you would shoes with a rag, a little work but it will polish the groove smooth, maybe not completely remove it, but you have to make it smooth so that it won’t catch a fingernail.
Then some will install the new seal deeper or shallower to position it so that it doesn’t ride in the old groove.

There is another way if the groove is deep, a machine shop can machine it down and sweat fit a “speed sleeve” which is a thin layer of very hard steel, which provides an excellent wear surface. In my opinion a speed sleeve is superior to a new part as the sleeve is very wear resistant.
A thin layer of chassis grease, not molybdenum won’t hurt on reassembly either, silicone grease is excellent for this, but molybdenum grease and many anti-seizes have fine metal powder in them that can be abrasive.
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Old 12-10-2019, 07:51   #3
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Re: Yanmar 4JH2-TE Crankshaft Pulley has a groove

Thank you!

I can get a replacement part from J-Way Enterprises for $168, including shipping. Don't think my local machine shop could machine it and fit a speed sleeve for that price, so I'll order a new part.

Next up: rear seal plus every gasket. I have the engine in my garage at home, on a stand, so working on it is really easy. The last time I did a complete rebuild, I was a teenager. I rebuilt a 1952 Buick flat-head six that had thrown a rod. What an education! But I had to work in a shed, with a grass floor and a couple of 4x4's to sit the engine on. And that thing was heavy!
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Old 12-10-2019, 07:58   #4
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Re: Yanmar 4JH2-TE Crankshaft Pulley has a groove

Another question (off-topic). Given the wear on that crankshaft pulley, do you think I should replace my piston rings and crankshaft bearings? The engine starts up easily and runs smoke-free, but I'm going to remove the head, lap the valves, replace the head gasket, etc. anyway. It's not that much more work to replace the rings and bearings. And I have all winter to do it.
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Old 12-10-2019, 10:31   #5
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Re: Yanmar 4JH2-TE Crankshaft Pulley has a groove

with the engine out I would replace rings and bearings, I would probably go further like a total rebuild, turn crank etc.
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Old 12-10-2019, 10:38   #6
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Yanmar 4JH2-TE Crankshaft Pulley has a groove

If it were me, I’d disassemble and inspect, and based on what I found make my decisions.
However even if you find it perfect, I’d still replace rings and bearings, and oil pump, and have the head rebuilt. Because cause for not much money you can start over with new clearances. I don’t even measure oil pumps, I go with new as I consider them just too important not to.

In my opinion in a Diesel the compression is too high for just a lap the valves thing, you want them done perfectly at a machine shop with of course new seals, head magnafluxed etc. just do NOT let them shave the head to clean it up, many shops want to and it can cause problems in a Diesel.
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Old 12-10-2019, 21:37   #7
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Re: Yanmar 4JH2-TE Crankshaft Pulley has a groove

Another option with the front pulley groove is the DIY "Speedisleeve". They come as a kit with a installing tool and you just whack em on with a hammer..... well, carefully tap into place. No machining necessary and as a64pilot pointed out, these things are hard to wear out. You can use the same genuine yanmar seal too because the speedisleeve is very thin walled. These are a real lifesaver on the rear crankshaft sealing flange too because the job can be done in a few minutes in situ rather than the tedious job of getting the shaft out to be machined.
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Old 13-10-2019, 18:05   #8
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Re: Yanmar 4JH2-TE Crankshaft Pulley has a groove

As much as I like speed sleeves, if I had the motor apart and a new part was only $168, I’d go new myself.
If I had my motor in the garage on a stand, no way I wouldn’t pull it apart and inspect and replace worn items either.
You should get another 20 years or more doing that.
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Old 14-10-2019, 07:54   #9
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Re: Yanmar 4JH2-TE Crankshaft Pulley has a groove

Thanks for the helpful comments, everyone. I haven't yet inspected the rear seal, because my engine stand is bolted to the bell housing, making it rather difficult to remove the flywheel. I will first need to put the engine on a couple of timbers on the floor, remove the flywheel and bell housing, then put it back on the stand. Fortunately I have an engine hoist, so this is pretty easy. Given the wear on the pulley, I expect to find something similar at the rear of the crankshaft -- so a Speed Sleeve looks like the way to go there. Curious -- why doesn't oil seep out under the speed sleeve? Must be a tight fit, I guess.

I do plan on tearing the whole engine down, with one exception: the fuel injection pump. I have no reason to suspect any problems with it, but is there anything I should do -- like send it out for testing?
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Old 14-10-2019, 08:36   #10
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Re: Yanmar 4JH2-TE Crankshaft Pulley has a groove

Do yourself a favor, find or build a heavy table to put the engine on.
Your back will thank you
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Old 14-10-2019, 18:05   #11
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Re: Yanmar 4JH2-TE Crankshaft Pulley has a groove

"Curious -- why doesn't oil seep out under the speed sleeve? Must be a tight fit, I guess."

Speedy sleeves work great. it will use a touch of sealant on the original spot and is a very tight fit.

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Old 14-10-2019, 19:21   #12
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Yanmar 4JH2-TE Crankshaft Pulley has a groove

I like to “sweat” them on, put the harmonic balancer in the freezer overnight and heat the sleeve and it will drop into place, but to get it off takes a Dremel to cut it to release the tension.

Learned that trick boring out drag bikes last Century, we would take 900 Kawasaki’s to as high as 1327 cc which takes another cylinder block and much larger sleeves of course. Freeze the sleeves and heat the block and it was a drop in fit, but once temps stabilized they weren’t coming apart.
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Old 15-10-2019, 15:14   #13
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Re: Yanmar 4JH2-TE Crankshaft Pulley has a groove

I do plan on tearing the whole engine down, with one exception: the fuel injection pump. I have no reason to suspect any problems with it, but is there anything I should do -- like send it out for testing?[/QUOTE]

If you have fed the engine with clean fuel I would not bother to touch the fuel injection pump. If you get it tested you have to know the shop is trustworthy as many of them have the default position of telling you it needs a rebuild as that is where the money is.
Whilst I don't know your engine I would have thought at 2700hrs, provided it hasn't had water or dirt thru it your injection pump should be fine.
Injectors would be worth checking.

Agree with hone, new rings, bearings & a valve grind if you pull it apart as other posters say.
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Old 16-10-2019, 13:12   #14
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Yanmar 4JH2-TE Crankshaft Pulley has a groove

I would send both the pump and injectors to a Diesel injection shop.
I always did when I rebuilt farm equipment, and as often as not they were fine, but did need adjustments to bring them back into spec. I believe without exception all had drifted out of spec, which affects timing and smoke / power output etc.
The injection pump plungers on my JD410 backhoe were scored so much the shop said he was surprised the engine would crank, but it ran fine.

People can and do “test” their own, but they don’t have the necessary testing equipment to determine the injectors crack at the correct pressure, which is usually adjusted by shimming and it does change with age, same for a pump.

In my opinion having things cleaned inspected and parts replaced as necessary is smart, it ensure the pump and injectors operate within new specs, why wouldn’t you want to do that if your going through all the trouble and expense of overhauling the engine?

Now I know of some people that also will replace the starter, water pump and even the alternator so it’s all new. I can’t bring myself to do that, but I do understand the argument.
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Old 16-10-2019, 13:30   #15
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Re: Yanmar 4JH2-TE Crankshaft Pulley has a groove

Folks on this thread clearly have a lot more money than me

No smoke, easy to start, no other ailments other than an oil leak at the crank pulley? On my motor I would machine a 3mm spacer to go onto the crank before the pulley so that the new seal runs on a virgin surface, put it back together and it’s good for another 5000 hours.

Your $2000 job would be my $100 job. But that’s just me . . .
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