Yanmar Oil Seal

[F10]

Looks like my Yanmar 3gmd crank oil seal (the one near the belt Pulley) is leaking. I have a maintenance manual on how to replace. Any advice or hints to do the job right? How do you remove the old seal? Is the seal all rubber or is the outside metal?
Thanks

[Lepke]

Don't know Yanmar, but most seals are metal sides and front, bonded to the seal. Some have metal inside the rubber. The seal is a tight fit and is pressed or tapped into the front cover. Often the easiest way to remove the old seal is to remove the cover and tap out from what was the inside. There are seal pullers made that look like a gear puller but with feet pointing out.
Since the seal is leaking, there is a destructive method. Using a punch, tap at the edge, bending the metal enough to get a pry tool into the gap created.
The leak can also be caused by an imperfect surface on the crank. Without repair it will continue to ruin seals. There are sleeves made to slide over the area where the seal rubs. Available at better bearing supply stores. Teflon I think.
If the crank is out of the engine, the old way to fix is hard chroming the area and polish to original size. Very durable and lasts the life of the engine.

[F10]

Thanks for information. I have a seal on order and will try to install.

[boatbod]

I once replaced the front seal on a Yanmar 4JH2 while at a marina some considerable distance from home with only basic tools. It's not fun, but definitely do-able without stripping the whole engine down.

Remove pulley, pry out old seal, clean, lubricate and drive in new seal.

[F10]

Originally Posted by boatbod

I once replaced the front seal on a Yanmar 4JH2 while at a marina some considerable distance from home with only basic tools. It's not fun, but definitely do-able without stripping the whole engine down.

Remove pulley, pry out old seal, clean, lubricate and drive in new seal.

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

[Frankly]

How bad is it leaking. The rear seal on my 3GM started leaking slightly years back as we were heading for the Bahamas. Purchased a replacement seal and a few other parts (figuring there was no Yanmar parts dealer at Waderick Wells) and off we went. 7 years the seal is still in the parts box. Now the front seal is leaking a bit but probably the two represent a 1/4 cup every oil change (100 hrs). My 3GM is now 26 YO and has 4000 hrs on her.

[a64pilot]

Originally Posted by F10

Thanks for information. I have a seal on order and will try to install.

If you replace the seal, inspect the crank closely, if there is a slight groove where the old seal rode on it, be sure to polish it out with some 800 or finer cloth. I like to cut it in 1" wide strips and polish it like it was a shoe if that makes sense.
If the groove is very deep then often you can set the new seal not as deep making it ride on a portion of the crank without a groove.
Most of the time the groove is slight and can be polished out, doesn't hurt to polish anyway even if there is no groove, your not removing enough metal to matter with polishing.

[F10]

Originally Posted by Frankly

How bad is it leaking. The rear seal on my 3GM started leaking slightly years back as we were heading for the Bahamas. Purchased a replacement seal and a few other parts (figuring there was no Yanmar parts dealer at Waderick Wells) and off we went. 7 years the seal is still in the parts box. Now the front seal is leaking a bit but probably the two represent a 1/4 cup every oil change (100 hrs). My 3GM is now 26 YO and has 4000 hrs on her.

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.

[Frankly]

Obviously you have started down the correct path as you have a problem that can't fit in the "when I get around to it" bin. Let us know how the replacement goes, a lot of us are on the same road/ rode just a little further aft.

[galynd]

Male sure it's not the timing cover gasket which has been a common problem with the 3gm30f models.

[a64pilot]

Originally Posted by galynd

Male sure it's not the timing cover gasket which has been a common problem with the 3gm30f models.

Even if it is, removal of the cover is required, oil seal is in the cover unless I'm mistaken, it is in most engines anyway.
If so I'd replace the seal as they get real old, sometimes the seal hardens and wears that groove into the crankshaft, so at that age it prudent to renew, in my opinion.

[a64pilot]

To find the leak I like to use rubbing alcohol in a spray bottle, alcohol isn't all that dangerous, evaporates and doesn't hurt paint or anything, but will wash away oil, once you get it clean, then you can find the source of the leak for sure.
Put paper towels down to catch the alcohol as it washes off.

[belizesailor]

Originally Posted by a64pilot

Even if it is, removal of the cover is required, oil seal is in the cover unless I'm mistaken, it is in most engines anyway.
If so I'd replace the seal as they get real old, sometimes the seal hardens and wears that groove into the crankshaft, so at that age it prudent to renew, in my opinion.

You can pry out and replace the seal without removing the timing cover.

[a64pilot]

Originally Posted by belizesailor

You can pry out and replace the seal without removing the timing cover.

Really? All engines I have done the seal is pressed in from the inside of the cover, I have always assumed this was so it couldn't come out in operation as that would result in a large oil leak.
I am not familiar with this engine though

[belizesailor]

Originally Posted by a64pilot

Really? All engines I have done the seal is pressed in from the inside of the cover, I have always assumed this was so it couldn't come out in operation as that would result in a large oil leak.
I am not familiar with this engine though

I think it can be done in the Yanmar from the outside...need to confirm though. Know it can be done on Volvo MD series.