YANMAR 3YM30 dumps oil into bilge

[mikequig]

A charterer returned my boat with the complaint that there was a major oil leak and that he had to add about 5 qts of oil to the engine. What a mess! After sucking most of the oil our of the bilge and engine sump pan I discovered a small metal and rubber thing in the sump pan. (see photo) I cleaned it up and took it over to a nearby marina engine shop and asked them what it was. "Looks like a dipstick," they said. "Nothing wrong with my dipstick," I said. Fortunately, they had a new similar engine outside the shop on blocks for sale ($8000!). I gave it a good going over and discovered what looked like an exact copy of what I found in my sump. Under the oil filter at the 4 o'clock position was what looked like a dipstick plug.(I had trouble rotating the photo 90 degrees) It seems Yanmar just plugged that hole when it moved the dipstick to a different location up forward - maybe for better access. Anyway, you may want to be be sure your dipstick plug is secure or else you might find a similar mess when your boat heels over on port tack!

[SVSlowRide]

Were you able to replace the old plug? Did you order a new one? Is it yanmar part number 124976-34850? There should not be much pressure (same as the dipstick). I wrapped some high temp emergency tape around the now hard rubber in order for it to stay in. Thanks for your post......

[model 10]

Holy moly.

[LAGO]

Jeez this just happened to me and I found your 5 year old post! Thanks for the explanation, probably saved me some money with the mechanic. I sucked about 1.75 litres of oil out of the oil pan under the motor and off the engine room walls!

[mikequig]

Sorry you had to experience this mess too. It’s a pretty easy fix, once you get things cleaned up but is should have been a better design in the first place. The hole should have been tapped and plugged instead.
M. Quigley

[Compass790]

Wow that sounds like great design!

I think I'd be drilling & tapping that hole for a plug or bolt.


Whoops posted whilst you were posting mikequig

[Ian Neale]

Hi, I have just had this same issue on my 13 year old Yanmar, thanks so much for the post it allowed me to quickly identify the issue ad put my mind at ease to the cause.

Crazy how Yanmar only plugs it with a rubber plug from a dip stick that deteriorates over the years and shrined allowing it to jump out. The plug on my engine literally rattled about in the hole in the side of the block.

[longjonsilver]

Originally Posted by mikequig

It’s a pretty easy fix, once you get things cleaned up but is should have been a better design in the first place. The hole should have been tapped and plugged instead.

This is what i did for a coolant passage on my new motor for my car, a 3/4 NPT tap for 20 buckarooz on amazon did the trick and i screwed in a plug with teflon tape. This is after seeing a friend with the same motor in his car stranded beside the road cuz he plugged it with a rubber stopper. That worked until it didn't.

jon

[jimbunyard]

I'm wondering if this doesn't mean the engines this happens to don't have either a clogged breather tube and/or a poorly designed crankcase venting system...

[Ian Neale]

In my case I don’t think there are any issues other than an old plug that the rubber had hardened and shrunk. It was very loose when I reinserted it. So loose in fact when I had someone restart the engine after refilling it with oil it nearly jumped out when the engine moved as the starter engaged.

I think it has been wobbling around in the hole just waiting the fall out as it did when we were dropping anchor and I revel the engine to set the anchor.

A very poor design indeed. Unfortunately on my boat you can’t get enough clearance to tap the hole and make a more permanent fix.

[jzk]

This just happened to me yesterday! I am ordering a couple of these. Thinking about tapping that hole and plugging it for good.

[longjonsilver]

Be careful when tapping a hole in an engine that you don't get filings dropped down into the engine. Stuff some rags in and then vacuum out the filings before removing the rags....

[jzk]

I found the plug. Fits very loosely into the hole. I carefully white taped it around the top of the plug only. THen I pressed it in good with a screwdriver handle. It just rattled out. It wasn't "blown" out. If there was such huge pressure down there, it would also be blowing out the dipstick.

I ordered 2 new ones.

[rgleason]

Thankyou Mike for posting.

[jzk]

Originally Posted by jimbunyard

I'm wondering if this doesn't mean the engines this happens to don't have either a clogged breather tube and/or a poorly designed crankcase venting system...

I was wondering that too, and the Yanmar guy said something about that as well. Mine was just sitting in the hole with nothing holding it. The dipstick is way easier to pull out. Further, that same pressure would push the dipstick up as well, as it is all connected to the oil pan.