Seal / Gasket compound for Fittings to Diesel Tank

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Kinsale373

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I've suceeded in pumping out my Diesel Tank and removing and cleaning it on my Bene 373. I was surprised at how clean the tank was for a 2004 boat. Just a cup full of Black Gunge at the end of the tank. It was so clean that I decide not to steam or power clean and instead rinced the tank well with clean diesel.
I used a RACOR Fuel Filter /water seperator Funnel to filter all my diesel and and it works well . I set it up with a small syphon (6 mil dia) from the "dirty can" feeing down to the Clean drum. and over 15 Mins filtered 20 Liters at a time. works well but keep an eye out for filter blockage or you'll have diesel all over the floor,
So once the storms goes through on Moday the tank does back in next week !
Question s: I noticed that when removing the threaded screws that hold the 2" Diameter plates to the top of the tank ( Used for entrance of Fuel pump and return pipes , Depth gauge and heater pipes. ) that the screws had some type of purple colored sealing material on each , like you would do with a screw through fibre glass. Has anyone a suggestion on what would be a good material to use to reseal the screws in the tank and maybe use a s a gasket meaterial beneath the plates ?

I'm wondering if I I should use the same material to get a good seal on the 2" Diesel filling pipe that goes onto a spigot at the rear of the tank? Or are the double Pipe Clips good enough ?. It as a wrestling match to get this connection off anyway? Still I dont want any diesel leaks .

Interested in your thoughts, Kinsale 373
 
You can get diesel resistant gasket sealant for the screws, halfords will sell it, the brand I know is called permatex although don't know if it exists over here. To seal the tank plate I ordered a small piece of nitrile mat of the internet and cut it to shape.
 
Kinsale373 said:
I've suceeded in pumping out my Diesel Tank and removing and cleaning it on my Bene 373. I was surprised at how clean the tank was for a 2004 boat. Just a cup full of Black Gunge at the end of the tank. It was so clean that I decide not to steam or power clean and instead rinced the tank well with clean diesel.
I used a RACOR Fuel Filter /water seperator Funnel to filter all my diesel and and it works well . I set it up with a small syphon (6 mil dia) from the "dirty can" feeing down to the Clean drum. and over 15 Mins filtered 20 Liters at a time. works well but keep an eye out for filter blockage or you'll have diesel all over the floor,
So once the storms goes through on Moday the tank does back in next week !
Question s: I noticed that when removing the threaded screws that hold the 2" Diameter plates to the top of the tank ( Used for entrance of Fuel pump and return pipes , Depth gauge and heater pipes. ) that the screws had some type of purple colored sealing material on each , like you would do with a screw through fibre glass. Has anyone a suggestion on what would be a good material to use to reseal the screws in the tank and maybe use a s a gasket meaterial beneath the plates ?

I'm wondering if I I should use the same material to get a good seal on the 2" Diesel filling pipe that goes onto a spigot at the rear of the tank? Or are the double Pipe Clips good enough ?. It as a wrestling match to get this connection off anyway? Still I dont want any diesel leaks .

Interested in your thoughts, Kinsale 373
Click to expand...
Possibly Hylomar Blue.

If this is the first time you have removed any tank fittings, I hope you manage to reseal successfully first time. Or that Beneteau engineered the tank better than jeanneau, though I doubt this.

Original gaskets probably nitrile rubber. After similar work on my own Jeanneau tank it took almost a year to get a proper seal: two different 'diesel engineers' failed. Eventually I sorted it myself with cork/nitrile gaskets coated both sides with Hylomar Red and fitting screws coated with Hylomar Blue to seal threads. Before settling on Hylomars tried other sealants, nothing else stopped weeps of diesel. Absolutely nothing sticks to polyethlene - you have to achieve a tight pressure joint to something that is not dead flat, rigid and smooth.

One of the problems I had was that Jeanneau had fitted the pipe fittings to the polyethylene tank with self-tappers. Once these had been undone and replaced a few times they ceased to grip: initial fix was slightly fatter screws. next time I needed to get into the tank I made a separate larger access hatch, and every fitting now has nuts and washers inside the tank. The access hatch has about 20 machine screws with a two-part tapped alloy plate underneath, pulling down firmly onto cork/nitrile gasket and both types of hylomar sealants. Not pretty but works: the sealants stay sticky where they ooze out.
 
Like the poster above I also had endless trouble getting a seal on a stainless tank and to cut a long story short I ended up cutting gaskets out of cork nitrile and used Hylomar blue for sealant around the self tappers in to the tank and fibre washers under the heads of the self tappers.
 
Kinsale373 said:
..I was surprised at how clean the tank was for a 2004 boat. Just a cup full of Black Gunge at the end of the tank. ..
Click to expand...
As a matter of interest, where is the boat kept, or more precisely, what fuel has it been filled with since new? It might be too much to just assume Kinsale!
 
When I need to create a new seal - as long as screws etc are able to bed completely without a gasket thickness .... then I use standard Hermetite gasket goo - BUT with an old trick ....

If you use it straight - it bonds both sides and then later you have the job of removing / cleaning up when servicing. So how to avoid that ? Smear oil on the fixed mating surface and into the threads of the screws ... apply liberal amount of Hermetite to the fitting and then screw it all together - make sure Hermetite shows all round the fitting as its closing up ... Leave it all in place to set .... touching the 'ooze' will give good indication when its good to use.
The oil prevents one side of the Hermetite from bonding - so later you can unscrew cleanly.

Often the trick with fittings is NOT to tighten down too hard. Second that tapered thread fittings are not designed to have thread tape ... common error.

Of course if you ca get suitable gasket material ... then sure ..
 
Guys , Thanks for a lot of very useful info.

The design of the entry point into the tank looks reliable enough. Its made by "Bonar Tanks" France. They have molded in a series of flat spots approx 2.5" in diameter towards the front of the tank. There are Qty 5 threaded studs molded into each plastic flat . These are designed to take machine screws. So to fit a pipe to the tank you drill an access hole in the centre of the flat spot and use machine screws to secure the new flange in place to the molded in studs . The system looks reliable and robust enough. You are sealing to a flat and what looks to be a solid piece of tank.

Hylomar Blue and Red and cork nitrile gasket seems to get most more votes , Ill try to locate some of this.

Thats a good trick to ensure you can open the Screws when required- thanks Refuller, I can see that being helpful,

The job has turned out to be a bit of overkill ok , I'd probable have gotten away with leaving well enough alone. As the boat is 2004 and new to me in 2015 (Purchased in France) , I hadn't a clue what was in the tank. To be honest I had a reasonable view inside the tank when I lifted off the Engine Fuel supply and return lines and the fuel gage flanges. These are seperate flanges. at the front of the tank. Once you pump out the diesel you , shine a torch through one ope and view through the other and would get a reasonalble view of what is left inside. I suppose you could sample the bottom of the tank with a manual fuel pump as was suggested to me' rather than pump out.
It wasn't a major job to get out my empty tank so I decided to do this and do a good rince out as described just to be sure.

Lessons learned:
I used a new 40L /min fuel pump purchased off the internet. I though it was self priming ! Not so. I have a small squeesy fuel pump with a meter of 6 mil tube that was invaluable for priming the main pump line. I also used this to syphon at a slow rate into the racor Funnel Filter / water seperator in order to clean the all diesel before re use.

I borrowed some 20 Litre clear plastic drums from a friend of mine who has mechanical diggers. The clear cans are great as you can see when they are nearly full and avoid spills.


Thanks again for the advice and inputs,

Kinsale 373
 
I use a Pela Oil Vacuum system.

Its the one designed to drain your sump oil by sucking it out via the dipstick hole.

To get my tank out would be a major job as its a truck tank ! mounted under the stbd forward bunk.
 
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