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Old 09-09-2014, 04:50   #1
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Yanmar 3GM30 Oil Leak

Just wondering if someone can tell me a most likely cause or perhaps suggest where to look. My engine developed a slight oil leak this season, which seems to be coming somewhere from the rear. Without some kind of mirror arrangement, I can't see the source of it. Any ideas or probabilities?
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Old 09-09-2014, 05:50   #2
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Re: Yanmar 3GM30 Oil Leak

If it's down low, it could be the rear main seal. First check to be sure the crankcase vent is clear, even a partially clogged vent can cause pressure in the crankcase and therefore an oil leak. Not saying this is it, but it's something easy to eliminate
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Old 09-09-2014, 05:52   #3
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Re: Yanmar 3GM30 Oil Leak

Thanks immensely. I will look at the vent first. If it's the main seal, are we talking engine removal to replace it? (Hoping not, of course.)
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Old 09-09-2014, 08:47   #4
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Re: Yanmar 3GM30 Oil Leak

most common place for leaks on 3gm's is the oil line running external from behind the
starter around the back of engine feeding the three main bearings. get a mirror. ole
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Old 09-09-2014, 09:00   #5
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Re: Yanmar 3GM30 Oil Leak

Thanks very much, Ole. I just ordered a telescoping mirror with lights from Amazon.
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Old 09-09-2014, 09:53   #6
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Re: Yanmar 3GM30 Oil Leak

The exterior oil line that runs behind the starter has a nasty habit of rusting between the oil banjo bolt and starter. A very common problem with the 3gm30's, (2gm's too) Yanmar has a new copper line replacement part for $54 ish.

I repaired mine with 1/8" copper tube (1900 psig burst pressure available at most hardware stores for 60 cents a foot or so), rerouted it to above the starter, so no messing with the starter, drilled out the banjo bolt and tee fitting at ether end and soldered the copper to them using a 450 degree F solder and flux.

Don't braze the copper as brazing will anneal copper above 900 degrees and cause it to fail rather quickly at the annealed joint. With copper tubing, soldering is your friend.

Check that the passages are clear after soldering. Strap the copper oil line to the injector lines and other locations to keep it from vibrating.

I've 200 hours on my oil line replacement, still going strong.
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Old 09-09-2014, 10:04   #7
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Re: Yanmar 3GM30 Oil Leak

Thanks, sailorchic. That's an amazing solution.
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Old 01-10-2014, 09:10   #8
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Re: Yanmar 3GM30 Oil Leak

Okay, I've removed the crankcase breather vent and the tube, and neither was clogged. I've gotten a lighted mirror and my fingers along the line running from behind the starter to the main bearings, and it is not leaking. I found a slight leak from the sternmost, port side corner of the oilpan and tightened the bolts about 1/8th, and that leak seems to have stopped.

Unfortunately, I still have an oil leak. It runs down the back of the engine block and seems to be coming from someplace where the block attaches to the flywheel housing. So, my question is: Should I do a compression test to indicate whether the rings are shot and then, if they are, should I assume that all seals and gaskets are fine and that the air being pumped into the lubrication system is forcing oil out through perfectly good seals, or should I go straight to replacing the seals (which is gonna get ugly)?
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Old 02-10-2014, 06:31   #9
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Re: Yanmar 3GM30 Oil Leak

Time for some pics i still think external oil line OLe
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Old 02-10-2014, 06:36   #10
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Re: Yanmar 3GM30 Oil Leak

Quote:
Originally Posted by olepedersen View Post
Time for some pics i still think external oil line OLe
I hear ya, Ole! Sorry I don't have any pictures. But based on your suggestion, I'll take another good, hard look with the mirror and run my fingers along the line again. I am no expert at these things. In fact, most of the time I'm at a loss and just flailing about. That's why I ask for help from people with much more experience than I have. I appreciate all the input.
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Old 06-03-2015, 17:40   #11
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Re: Yanmar 3GM30 Oil Leak

My new to me 3qm30 is exhibiting an oil leak in what is probably the same line. It comes from behind starter around back of block and then banjos into the head alongside the exhaust manifold. While I admire SC's fix, I am probably looking to replace the part. Anyone know if the exhaust manifold has t o come off? I am also looking for a part number. My other question would be to ask if a fix could be developed using compression fittings like this: http://volksweb.relitech.com/tech/brakeln/compft2.jpg
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Old 06-03-2015, 21:23   #12
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Re: Yanmar 3GM30 Oil Leak

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Originally Posted by rbyham View Post
My new to me 3qm30 is exhibiting an oil leak in what is probably the same line. It comes from behind starter around back of block and then banjos into the head alongside the exhaust manifold. While I admire SC's fix, I am probably looking to replace the part. Anyone know if the exhaust manifold has t o come off? I am also looking for a part number. My other question would be to ask if a fix could be developed using compression fittings like this: http://volksweb.relitech.com/tech/brakeln/compft2.jpg
You do not need to remove the exhaust manifold to replace the banjo bolt under the manifold. But it helps if you unbolt the fuel filter to get access to the banjo bolt. You may need to remove the starter too as the clearance is pretty tight with the OEM oil line.

In theory the compression fittings would work, but I think you'll find that several inches of the existing steel line is bad.
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Old 08-03-2015, 22:39   #13
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Re: Yanmar 3GM30 Oil Leak

sorry to say its now just a snow ball affect. pull it. leaking engines are bad engines.
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Old 08-03-2015, 22:50   #14
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Re: Yanmar 3GM30 Oil Leak

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Originally Posted by DennisM View Post
I hear ya, Ole! Sorry I don't have any pictures. But based on your suggestion, I'll take another good, hard look with the mirror and run my fingers along the line again. I am no expert at these things. In fact, most of the time I'm at a loss and just flailing about. That's why I ask for help from people with much more experience than I have. I appreciate all the input.
Hum. so experiment time. With the engine running open the oil fill, does pressure come out, any smoke. A possibility is the breather is clogged and oil is leaking around the breather assembly which is at the back of the engine.

Does the engine start easy. Is there grey smoke when the oil fill cap is removed.
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Old 05-06-2015, 11:00   #15
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Re: Yanmar 3GM30 Oil Leak

Quote:
I repaired mine with 1/8" copper tube (1900 psig burst pressure available at most hardware stores for 60 cents a foot or so), rerouted it to above the starter, so no messing with the starter, drilled out the banjo bolt and tee fitting at ether end and soldered the copper to them using a 450 degree F solder and flux.
Sailorchic-my steel line measures .188 dia. Do I want 1/4" OD (1/8" nominal) or 1/8" OD? Sorry to be so anal....Ed (with a 2GM20)
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