Slow Diesel Leak

[dmbraaten]

I have a slow (3 liters a year) diesel leak that is more evident during warm months than cooler months. This started after a voyage from Alesland, Norway where I purchased her down to Varazze, Italy where she is now.

The previous owner never noticed anything while she used it for 8 years all in the north sea and I had her in the summer in the Netherlands and did not notice any leaking then.

It started when rounding Portugal as we notices small amounts of diesel coming from the weep hold below the pan for the engine (I have a single John Deer). I have had her in Varazze for a couple years and all is ok during Nov - Feb then the leak starts up again once it gets warmer.

The attached pictures attempt to show where the leak is coming from. It is not coming from the engine or hoses or anything on top of the GRP pan under the engine. It is coming from under the pan via the port side weep hole that allows water to pass from the shaft area to the forward so it can drain at the engine sump pump.

I have 2 GRP tanks each holding 2,500 liters. I suspect I have a stress fracture in the port tank and diesel is passing through, under the floor of the engine room along the stringers and finally coming out under the pan since this is a normal exit.

Hope all that makes sense. I attached a couple pics and some info on Selene hull lamination.

Questions - has anyone had anything similar? Any ideas I haven't listed? What about having the tanks re-glassed? I would do both if I have to do one.

 

[PM]

Three liters a year is not much. It is a leak, to be sure but not critical at this point. If it were my boat I would literally pack the area with oil absorbing pads. Over, under around and through. In a while you should be able to locate the source. In the mean time you are not causing a sheen on the water and you are buying time until you win the lottery.

I wish I knew the year of your boat. the bilge is so clean and well maintained it might be a small matter.

pete

 

[moparharn]

Does the condition change with fuel load? If the tanks gets below half full does the leak stop? There appears to be a stress fracture in your stringer where the green line is directed over the top of it. Does this fracture go to the tank? I would use a fluorescent dye added to the fuel tank and then locate the trail with a black light. Thermal expansion of the GRP should seal the leak and not make it worse. I am not sure if diesel expands much with heat, but this is something I would want to know more about. You must first identify every penetration of the tank and eliminate them as possible sources. That stringer crack is suspicious (I am assuming it is a stringer by its appearance, but the photo does not contain its actual location). The crack also appears to have been repaired towards the bottom. Leaking fuel is not something I would ever tolerate regardless of the assumed risks. Good luck with your sleuthing.

 

[rgano]

Even a drop of stray diesel in my engine room is more than I can tolerate, and three liters a year is going to stink up the boat big time and affect resale value. You have clearly identified the problem as a tank related leak rather than the easier to handle engine-related type. Thank your lucky stars it is not a gasoline boat! In regard to how to diagnose, I think moparharn's advice is the way to go, especially the dye idea. Hope you will let us know how it all goes and that you will share your Italian boating experiences with us. Welcome aboard.

 

[jungpeter]

Hi dmbraaten,

I, like Rich Gano, believe fuel tanks should not leak AT ALL. It's like being pregnant. You are, or you aren't. And no boat of mine will ever have leaky tankage. Stinks, causes a cosmetic mess, is a potential safety issue, and is an obvious sign of a fundamental flaw in your boat. It's your boat and your choice, but if I owned your Selene, I'd be on the phone to the factory ASAP to elicit their assistance in fixing the issue. And I'd be pretty loud about it. At least Selene Yachts is still around.

Given the presence in the EU of a large number of boatyards and fabricators with extensive experience with high-end composite construction and repair (megayacht yards, for instance), hopefully you can locate someone to take care of your tanks.

Best of luck in fixing THIS one. It's a "sticky wicket" for sure.

Regards,

Pete

 

[Lou_tribal]

I had something like this once because I was idiot enough to fully top up both of my tanks (think about fuel return...) so one tank was slightly over filled and the leak was at the tank vent fitting. It was a tiny leak going all around the tank and through a tunnel like yours to end in the bilge. Not much but enough to be seen as a shiny trace on the bilge paint.

L

 

[sunchaser]

Suggest you carefully trace and monitor all lines, valves and hoses going to and from the tank. This would include engine feed, engine return, fuel transfer, fuel manifold and polishing plumbing.

You want to 100.00% eliminate any of the literally dozens of the above items as potential leak spots. Some years ago I had a very hard to find fuel weep that was due to an in line check valve nylon washer failing.

 

[C lectric]

Checking hoses, connection points and fittings for leaks/weeps can be helped along by the use of the Scot blue paper shop towels.
Any moisture will produce a distinct colour change that white towel will not.

 

[dmbraaten]

Thank you for your responses. Here are some additional points/answers to questions.

The year of my Selene is 2008. The engine room is almost as clean as an operating room. The previous owner was just as OCD as me . (see pics)

We did fill up almost to the top on one trip as the diesel was so cheap. I was wondering if this might cause problems given all the pressure in tank when full. So this may have been what caused a stress crack/leak if there is one.

The leak may be a bit stronger with more fuel in the tank. Problem is that it is not consistent. I use 2 tampons to absorb the fuel and these are check every 2 weeks. Fuel is not leaking every time and can go for a few weeks without anything, and then the tampons will need to be changed every other week (see pics). BTW, the leak is there even as she sits in her slip. Running the engine does not seem to make things better or worse.

I could probably deal with it as it is but am concerned that the stress crack (if there is one) will get worse and then I will have a big problem. So this is my main motivator to get it resolved.

Next steps when I can get there as Italy is locked down again:
- Look at every fuel line for cracks and wrap in blue paper towel so see if I get any moisture. Eliminate these as a source.
- Use two different color dyes but start with port tank to see if the diesel is coming from the tank. I assume it is the port as it is coming from the port weep hole. Will use different color for starboard. This will tell me for sure the leak is coming from one/both of the tanks.

If it is clear that the fuel is coming from either/both tanks, I think the only resolution is to have them re-glassed but would welcome other ideas.