Fuel tank leak

Bouba said:
This morning’s update
There wasn’t as much fuel to pump out as before





That container of fuel still had a couple of inches in it from last time. I guess that there’s a litre extra which is way down on its normal flow. My fuel gauges (for what they are worth, never found them that useful before)
Still, fingers crossed
The fuel is definitely not flowing aft from the tank. It must be forward then under the liner and in the hull and then aft.
It’s so cold and windy. I’m sitting in the toasty Tesla and I am calling it a day. I will go back in a couple of days and check if it had truly stopped flowing
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It does seem to be behaving more like a tank leak now. Starting off with lots in the bilge and then slowing down to a trickle over a period of time. It shouldn't take long to remove all hoses from the tank and cover all ends with something, even just a rag. Monitor the flow and add more fuel to the tank if it does stop. I'm pretty certain that it must be the tank if you disconnect it and the flow either continues or only starts again after a top up. You could pay someone to diagnose the fault and I bet they'd do exactly the same thing.
 
Mistroma said:
It does seem to be behaving more like a tank leak now. Starting off with lots in the bilge and then slowing down to a trickle over a period of time. It shouldn't take long to remove all hoses from the tank and cover all ends with something, even just a rag. Monitor the flow and add more fuel to the tank if it does stop. I'm pretty certain that it must be the tank if you disconnect it and the flow either continues or only starts again after a top up. You could pay someone to diagnose the fault and I bet they'd do exactly the same thing.
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Yes, after monitoring it for a few days more, if the flow has stopped and if the Beneteau engineer hasn’t arrived by then, then filling the tank with ten litres and measuring how much comes out should tell me a lot. If I remove the sender and put a dipstick in then I could get the level.
Of course, the hole could still be at the bottom but now is clogged with debris ?‍♂️
 
If you take the tank out whole or you can lift it enough to get all around it?

Fit an air feed to the tank that is ait tight with a pressure gauge ie airline to compressor, valve, pressure gauge tank. blank off all other apertures, soapy water over tank seams pressurise to no more than 2psi see if you can hold the pressure or where where it leaks.

If you have an inspection hatch and can see inside look for evidence of fuel contamination , black dust, black slime, water etc this is corrosive and attacks the aluminium tank.
 
Bandit said:
If you take the tank out whole or you can lift it enough to get all around it?

Fit an air feed to the tank that is ait tight with a pressure gauge ie airline to compressor, valve, pressure gauge tank. blank off all other apertures, soapy water over tank seams pressurise to no more than 2psi see if you can hold the pressure or where where it leaks.

If you have an inspection hatch and can see inside look for evidence of fuel contamination , black dust, black slime, water etc this is corrosive and attacks the aluminium tank.
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I think it’s possible to lean the tank forward, but I don’t want to do that myself (just yet). But it would depend on if there are fixing points that I can’t see or reach. If the hole was on the other side then it may just become visible. But if the hole is at either end or the bottom then it might not help me.
At this moment, I’m hoping that the Beneteau people have a trick to do this. But if it gets to the stage of being 90% sure it’s the tank even if I can’t find the hole. Then I would want it replaced (with a better one).
 
In fact, taking the old tank out is probably the only way I’m going to be able to clean and eliminate the smell. My guess is that the engine room sound deadening foam that the tank is leaning against will need replacing.
 
The Engine room foam insulation wicks up diesel, any that has been in contact will need to be removed cleaned up the area and replaced, various people do self adhesive insulation panels, including Volvo Penta.
 
Bandit said:
The Engine room foam insulation wicks up diesel, any that has been in contact will need to be removed cleaned up the area and replaced, various people do self adhesive insulation panels, including Volvo Penta.
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My feelings exactly
 
seastoke said:
Well it would be sucking air in wher preasure could push shit in the hole and block it .
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There is no shit in the tank................. its a fuel tank not black water ..............joking aside I don't think a pressure or vacuum test is a good idea, it may put all kind of stresses into the tank walls and the welds.
 
Bouba said:
Ok, this is the situation....the boat yard is unpaved, it’s gravel, it’s mud, it’s puddles. My car is brand new. My car is clean.
Also I am nursing my back after slipping down the outside stairs in the rain (I am feeling a lot better, thank you all for your sympathy (I mean that sincerely) touch wood). The boat is on the hard. The ladder has to come out of the car boot and be set up and I have to climb it. When all is wet an slippy I don’t feel good (flashbacks, post traumatic stress). Today is now good but lots of water came down yesterday, last night and this morning so the wife has persuaded me to go tomorrow morning instead. It didn’t take much persuading to be honest ??
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Wuss.
 
Vacuum testing a tank , how do you see a leak other than it has one because it the vacuum drops?

Shit in tank, would be fuel bug, which is corrosive to an aluminium tank.
 
Bandit said:
Vacuum testing a tank , how do you see a leak other than it has one because it the vacuum drops?

Shit in tank, would be fuel bug, which is corrosive to an aluminium tank.
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surely the same applies on preasure as he cannot see the leak now.
 
You have to lift the tank, blank off all openings except an airline and gain access all around it to do a pressure test, on board the boat or in a workshop.
 
Bandit said:
You have to lift the tank, blank off all openings except an airline and gain access all around it to do a pressure test, on board the boat or in a workshop.
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Good morning Bandit, if I get the tank in the workshop I would replace it with a stainless one (if I can source one). I’m not sure I would return a patched up ally tank or even if it turned out to be perfect.
To find the leak in situ is probably possible (for a more agile person) an empty tank could possibly be lifted an inch and dragged forward an inch. I have the necessary lifting bags and the endoscopes to look under and behind and a compressor for the experiment.
Getting the 250 litres of fuel out is difficult, I will probably have to buy lots of jerrycans. I actually have lots around the house but they are quite old now. The metal ones are probably still good but all my plastic ones are probably no good now.
 
Bouba said:
So following on to the previous post...where can I source a new 800l stainless steel tank from?
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Not sure how you are fixed in your part of the world but if it were me I would be having one made to measure but we do have several marine stainless outfits in our neck of the woods.

Not stainless but this outfit are pretty good - we had one of their holding tanks, which I installed on a previous boat tek-tanks
.
 
I am afraid that Bouba is in for a torrid time of it. Even if it isn't the tank it looks as though fuel has found it's way between the liner and the hull so unless there is a way to clean that space from above if he doesn't want a persistent smell of diesel in the boat it is going to have to be tank out and perhaps engine, cut away the liner thoroughly clean then rebound and glass the liner back into place. A new tank will be the least of of his worries and expenses.
 
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