Yanmar 2gm mystery oil leak

[mcaswell]

I pulled the engine cover off this evening to check the oil, and was surprised to see a sizable pool of fluid below the engine. Looking under the engine, I could see one drop hanging on near the back of the oil pan. Examining the pool of fluid, it was slippery, and seemed maybe slightly thinner than motor oil, but it was RED.

My first thought was that perhaps the previous owner had put ATF in the transmission (it's red, isn't it?), but I took a sample of the transmission oil from the dipstick and dabbed onto a paper towel, and it looked the normal brown color.

If it's not engine oil, and it's not transmission oil, what else could it be?

Dumb question, but what does diesel fuel look like? I confess, I've never seen diesel out in the open before... is it red? This fluid did not have a strong diesel smell, and it was thicker than I would expect diesel to be (but again, I could be wrong there, sine I've never touched diesel).

--Michael

 

[Mike Holibar]

ATF would be the usual oil for a 2GM trans. Try a dab from the pool on your tissue and see how it compares to your trans sample for color. The location of the drip, back of the oil pan would be a bit unusual for a trans leak. Front shaft seal would drip down the bell housing, then there is the rear seal and selector shaft seal, any of which could leak but not by the oil pan. The other possibility is an oil distribution line that runs across the back of the engine above the bell housing. These are prone to rusting out but it would not explain the red color. In the end you can only check the levels and if OK run the engine and see if you can trace the leak. If there is nothing obvious check the levels every half hour or so and if trans or eng oil level drops, you have found the source. Good luck,

 

[petersea]

Double check you manual but I believe that motor oil (30 weight) is the recommended fluid for that transmission. Diesel fuel is kind of a yellow/gray color unless it is dyed red for the fuel tax issue so depends in where you purchased it. Diesel will be about the same consistency as engine oil or AFT so that is not a good way to check. My suggestion is to change oil in trans and clean area when it leaked and check it often when running and after having run to see where it is coming from. It could be "red" diesel so check all the fuel lines and pumps and filters for leaks but usualy a fuel leak will also present a problem with air in the system and either hard or not starting. Good Luck keep us posted on what you find.

 

[Mike Holibar]

Pete could be right about the gear oil. I have a Yanmar 3HM with Kanzaki box, and a Perkins m50 with Hurth box and both run ATF. But check the manual to be sure.

 

[cbsailor]

Re: Leak

The 2GM uses 30W motor oil in the transmission. I doubt your leak is coming from there. Off road diesel fuel is red in color. The diesel typically sold in marinas is a #2 fuel with the #164 red dye added. The color indicates it is being sold without the "highway" tax added into the cost. It's a no-no to use this fuel in vehicles on the highway.

I would check for fuel leaks in the lines, banjo fittings and other connections.

 

[Don S/V ILLusion]

Rather than theorize, how does it compare in color with the diesel fuel in your tank?

 

[mcaswell]

ATF would be the usual oil for a 2GM trans. Try a dab from the pool on your tissue and see how it compares to your trans sample for color.

As others have mentioned, this motor doesn't use ATF (though the Yanmar manual I have states that some other motors, like the 3gm I believe, do use ATF).

I did do a comparison of the leaked oil and the oil that's in the transmission, and they don't look the same (transmission oil is grayish brown).

--Michael

 

[Clark]

2GM20F's of that vintage take 30W engine oil. Yanmars apparently like to 'weep' diesel into the collection area under the engine - I have a 1996 2GM20F that does just that and am planning a 'leak hunt'. I will probably replace all the banjo washers I can get to along with the secondary filter since fuel collects on the bottom of its bowl too.

 

[Clark]

Michael, I just saw your followup post. If your tranny oil is greyish-brown; you probably need to change it. I did mine 2 years ago and the oil is still clear under admittedly light use.

 

[mcaswell]

Well, the fact that diesel is thicker than I thought it was, combined with the red dye possibility (I did fuel up with marina-bought diesel), makes sense now.

I'm planning on heading back to the boat this afternoon to do the oil change, and will bleed out a little fuel to see if it matches (should have done that last night).

--Michael

 

[mcaswell]

Michael, I just saw your followup post. If your tranny oil is greyish-brown; you probably need to change it. I did mine 2 years ago and the oil is still clear under admittedly light use.

Thanks. Just to clarify, the oil is clear... when I said it was "grayish brown", I meant that it just slightly darkened the paper towel with that hint of brown color (as opposed to the leaked fluid, which darkened the paper towel with a reddish tint).

In contrast, the engine oil is opaque, and definitely needs to be changed (which I'm doing today). However, I'll probably go ahead and do the transmission oil too, since I don't know when it was last changed.

--Michael

 

[Cpt. Jon]

I purchase off-road diesel for my boat, it's not taxed the same so it's cheaper and it's better for the engine. Since they don't intend this for regular road use, it is illegal to fill your car/truck with this for road use, they put red dye in the deisel. If it looks like deisel and smells like deisel, it might just be deisel .

 

[sailaway78]

Fuel return line

First thing I would check would be the fuel return line. It connects at the rear of the injectors, and goes back into the tank. These seem to be a problem, at least for me. Where the hose connects to the fitting, the barb is short and I have had the line come off a couple of times.
The Yanmars return a very small amount of fuel, so a slight fuel puddle back there would be a good indication the return line is off.

 

[Don S/V ILLusion]

I purchase off-road diesel for my boat, it's not taxed the same so it's cheaper and it's better for the engine. Since they don't intend this for regular road use, it is illegal to fill your car/truck with this for road use, they put red dye in the deisel. If it looks like deisel and smells like deisel, it might just be deisel .

Could you explain why you say "it's better for the engine"?

 

[Deadline]

My Yanmar mechanic insists that ATF is recommended for the tranny. Go figure.

 

[Clark]

The type fluid is dictated buy the transmission. Our 280 has the 2GM20F with the Kanzaki KM2P trans.

Check this link out with your tranny model in hand . .

http://www.yanmarhelp.com/i_box2.htm

 

[mcaswell]

After looking at a sample of my diesel fuel, I do believe it's the same fluid that I saw underneath the engine. However, after doing the engine oil change this afternoon, I ran the motor for a good 30 minutes, and didn't observe any leaking. But the return line suggested by Nice N Easy as a possible culprit did look rather suspicious... the hose doesn't look like it's on the fitting as straight as it should be. I'll adjust that, and will continue to monitor for leaks.

--Michael

 

[Steve Dion]

Deadline: Did you ask your diesel mechanic if he/she was certified Yanmar?

 

[Hermit Scott]

See if it burns like diesel fuel.

 

[Cpt. Jon]

Could you explain why you say "it's better for the engine"?

I can't remember the exact reason, something to do with an additive that they don't add or something that they remove from the diesel sold for road use. I think it's sulfur, and I think that diesel engines like sulfur and I think the they do not add or perhaps they remove the sulfur from the on-road diesel. I believe that if you use on-road diesel that you are supposed to add an additive to it.

I just a computer geek sailor, so I could be wrong, this is just my understanding.