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Old 13-06-2017, 17:11   #16
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Re: Yanmar Oil Seal

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Do you need to drain engine oil prior to removing seal? Also, what is best way to remove old seal without damaging the crank?
Thanks
Generally no need to drain the pan for a front seal. You might for a rear seal if there is an appreciable angle on the engine needs.

Prying out is matter of experimentation. Can't quite remember what I used - picks probably, screwdrivers and needle nose pliers maybe.

The crank will be hardened so you are unlikely to damage that. The housing is however soft aluminum, so be careful there.
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Old 13-06-2017, 17:40   #17
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Re: Yanmar Oil Seal

Right, wrong or whatever.... In the past, I've screwed a small sheet metal screw into a lip seal and then pull with a set of vice grips. Of course, make sure you don't score anything.

Matt
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Old 13-06-2017, 18:06   #18
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Re: Yanmar Oil Seal

On the 3GMD engine to remove the 'timing cover' you have to take off the injection pump, and as ya'll all know that entails a bunch of other stuff. Luckily the seal installs from the front, so if you can get the old one out, the new one can be carefully tapped back in, with a square cut section of pipe of the appropriate diameter, or even a block of wood, with commensurately more care to ensure that it is square in the bore.


Unfortunately, this makes it impossible to polish the shaft, so your only options if the shaft is grooved are a speedisleeve or similar, or trying to position the seal in a different location in the housing so the sealing surface contact is in a different location on the shaft.


Another option for removal of the old seal is to drill a couple of small holes on opposite sides, sized to fit a sheet metal screw, screwing them in and using a notched prybar to lever the seal out. There is no 'best' way of doing this; the situation, your abilities and the tools available to you are going to dictate the most expedient approach...

And no, I've not done this on this particular model engine but have formed this opinion about it from looking at this parts breakdown.

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Old 15-06-2017, 01:52   #19
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Re: Yanmar Oil Seal

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Originally Posted by funjohnson View Post
Right, wrong or whatever.... In the past, I've screwed a small sheet metal screw into a lip seal and then pull with a set of vice grips. Of course, make sure you don't score anything.

Matt
+1

If you can see the seal with the pulley off you can use this method. It does work better on metal ringed seals if you use a pin vice and drill a small hole to guide the screw.

If the crank land is scored badly you can usually get a speedy seal to go over the groove and restore the running surface.

Cheers Tom
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Old 20-06-2017, 13:48   #20
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Re: Yanmar Oil Seal

Thanks for all the comments and Jimbum posted, the seal will come off by removing crank pulley (one nut holding that) and the seal is exposed. I have the new seal and it does have the metal outer ring and inner rubber seal with the circle spring on the inner groove. One could remove the cam cover housing and then remove the seal, however that could open up another can of worms for a nearly 40 year old engine working in a marine environment.

I am a little hesitant to go and pry or drill/screw the seal out as I am afraid I could score the crank or housing and render the engine a loss. I have good mechanical skills and have replace the head gasket on this engine, but not skilled at removing oil seal. I might consider paying a skilled mechanic to do the job, if I can find one. Rather spend $100 than potential ruin the engine (or create a lot of damage that is difficult to repair).

On pressing the seal in, another method may be to use the crank nut and a large washer, and short length of correct diameter pvc pipe to press the seal in- read about this method on-line.

One thing a little concerned about is potential corrosion between the metal part of the seal and the aluminum housing, seeing at times sea water would make its way to that area, if there were a minor sea water leak (engine is direct sea water cooled).

Again, thanks for all the comments and help
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Old 05-01-2018, 08:37   #21
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Re: Yanmar Oil Seal

I had a significant leak on my rear (flywheel side) 2GM20 at about 800 hrs, probably due to the PO letting salt water get into the bellhousing, was a bitch of a job to get the saildrive off and I replaced the flex plate. We put on a new seal which was fine for a while but now leaks when under a heavy load for a while, about 1600 hours.
Any suggestions how to polish the shaft in place? There is not a lot of room to work with. And is there some return drain line that might be plugged, resulting in more leakage while under a heavy load.
And anyone know the PN for a generic seal? I will buy 2 this time.
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Old 05-01-2018, 11:17   #22
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Re: Yanmar Oil Seal

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My seal leaks about 1/4 cup every hour (seal near main pulley). In the past I have noticed a few drips of oil after running for an hour but now the leak has increased. Engine in 1980 3GMD, so 37 years of use, not sure if previous owner may have changed seal.
I might recommend checking that the crankcase breather is clear. A 1/4 cup and hour leak seems pretty large in an area that is not normally pressurized.

BTW no seawater at all, in the from cover of a GMD or gm series engine.

One issue is the front nut is torqued on fairly high. So you need some method to keep the crank from turning. I used a screwdriver jammed on the flywheel gear through the starter opening (two people operation sometimes)
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Old 05-01-2018, 11:21   #23
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Re: Yanmar Oil Seal

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Any suggestions how to polish the shaft in place?
Remove the rear crank bearing retainer (6 bolts if I remember) then you have easy access to the rear crank bearing surface. You will need a new paper gasket for the bearing retainer.

The crank will be supported by the two inside crank bearings. Removing the bearing retainer makes it easy to replace the seal too...
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