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Old 12-04-2019, 08:33 PM   #1
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Hawkeye's Avatar
City: San Francisco Bay and Delta
Country: USA
Vessel Name: Happy Clown
Vessel Model: Heritage 45 Europa
Join Date: Jan 2016
Posts: 77
NESTE-branded plant-based diesel

I've been chasing a couple of diesel leaks since topping up in late Sept. Finally, I removed all the paneling around the six 110 gal tanks and got to the bottom of the problem. One leak is in a microscopic weld "failure" at the bottom of a tank, at a ball valve connection. The second leak is tiny, through threads of a nipple connection at the bottom of another ball valve fitting. These two leaks (and I hope no more) came immediately after adding 200 gallons of this stuff, on top of 400 gals of conventional fuel already in the tanks so it is pretty well diluted. My tanks are 18 years old, 5052 aluminum built by a reputable company.

I blame this product, whose technical data I finally got from their Houston office. (Sorry, not a hot link.)

Two relevant points for me are made in this document, 1) that this fuel is less dense than conventional diesel and 2) that the plant-based fuel is known to "cause leaks" in fuel systems more than 10 years old (perhaps because it is less viscous? I'll leave it to the fuel chemists and other experts on TF to make any connection between the two.) Note than this fuel is not conventional bio-diesel. It is from combustible waste, including food waste and it is said to have a chemical make up identical to #2 diesel.

At this time this fuel is only sold in California. Is it coming to the rest of the country? Because it is slightly cheaper (.05 gal) and has environmental benefits compared to good old #2 I believe that it will soon be sold far more widely than just California.

My fuel supplier for many years, Pittsburg Marina (a city-owned outlet in the Ca Delta area,) changed to this stuff a few months ago without telling their customers of the change. Had I known, I would have avoided it and willingly paid the $.05 additional until the stuff proved itself in key applications (like 10+ year old boats.) Now, I worry not only about the fixes for the two leaks I've located but the potential that new leaks keep appearing.

So, a heads up to all.

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Old 12-08-2019, 01:40 PM   #2
C lectric's Avatar
City: Gibsons, B.C.
Country: Canada
Vessel Name: Island Pride
Vessel Model: xxxx
Join Date: Oct 2007
Posts: 2,631
Good warning.
The same was said of Biodiesel many years ago, that it caused leaks and would damage seals. Also that it would loosen diesel varnish that had collected in the tanks and systems clogging filters and injection systems.
For many of us now Bio cannot be avoided easily or at all anymore.

Your leaking fitting can be fixed with a disassembly and resealing of the fitting, Of course the tank will have to be drained below the level of the fitting. Clean the threads thoroughly mechanically, then use a solvent and then use a sealer like Permatex #2. It's messy so lay some paper towels below to catch drips as you work.

The weld porosity may be more difficult but should be repairable by draining the tank completely, cleaning the porosity by use of air pressure to blow any liquid diesel out, then a solvent like toluene or acetone. Apply the solvent to the porosity letting it pull in and sit. Keep it wet. Blow it out again and reapply several times to allow the solvent to dissolve the remaining varnished diesel.

THen seal that porosity with Loctite 290 which is a wicking Loctite product. It will pull in and seal the porosity. Allow it to set for a day or two and the leak should be stopped. I've done this on other pieces successfully. The 290 is not usually stocked by auto parts places so may have to be ordered. I got mine from our larger local industrial supply house many years ago.
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