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Old 25-06-2020, 22:25   #1
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Cork Gasket for Diesel Tank Inspection Port?

In the process of learning more about my fuel system, figuring out where a clog in my fuel lines came from, and then deciding to clean the tank, I found out that some previous owner had an inspection hole cut into the side of the tank. I don't know much about fuel systems, so bear with me.

There's some sort of cork material gasket that was "glued" to the aluminum with a compound I couldn't identify:


I was wondering:
  • Is cork the right gasket material for diesel? There was some very minor leakage.
  • What sort of glue/compound would you use to attach the gasket to the aluminum?
  • Is there a reason something like silicone or butyl couldn't be used instead of cork? Does it degrade in diesel, or something?
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Old 25-06-2020, 23:49   #2
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Re: Cork Gasket for Diesel Tank Inspection Port?

Our boat's diesel tank had similar gasket material, albeit for an inspection hatch on the top rather than side of the tank. It was originally tacked in place with what looked to be a bit of silicone, but couldn't see the need for that so cleaned it off to ensure it never broke away and clogged a fuel line; I'd always suspected the 'cork like material' was used because it definitely didn't decompose, whereas many sealants would - OK if you/your mechanic uses the 'right' type, but a world of trouble if some cowboy doesn't.
Even on a vertical face there's no reason that you can't 'hook' the gasket over a couple of fixing screws to locate it place until you bolt it up, so don't have to glue it with anything.
Can't comment on butyl tape/diesel interaction, though I do know the tape doesn't like petrol on it.
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Old 26-06-2020, 02:33   #3
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Re: Cork Gasket for Diesel Tank Inspection Port?

I installed an inspection hatch on our boat. I bought it from Tek Tanks UK. I met the president of the company at METS Amsterdam. He explained me that they used cork because it was the only gasket material not being attacked by all the "diesel improvement" chemicals they put in diesel fuel these days.
Do not use butyl, it will dissolve in diesel fuel!
I also use "Hylomar Blue" as gasket goop for diesel tanks.
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Old 26-06-2020, 16:04   #4
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Re: Cork Gasket for Diesel Tank Inspection Port?

I was wondering:
  • Is cork the right gasket material for diesel? There was some very minor leakage.
  • What sort of glue/compound would you use to attach the gasket to the aluminum?
  • Is there a reason something like silicone or butyl couldn't be used instead of cork? Does it degrade in diesel, or something?
[/QUOTE]

Unusual to see a side inspection plate in boat tank.

Cork is ok but you can use Garlock or viton o-ring material. You dont need any sealant with those & you can hold an o-ring in place with superglue & glue the o-ring together with it as well. I would put garlock or o-ring inside & outside the fasteners.

If you use a cork gasket you can use Heldite, Hylomar, Stag or Loctite 518 flange sealant. There are many others, Permatex will make one for fuel too.
If you coat both sides of the gasket & both sealing faces with sealant you should have no problems. Or follow the directions
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Old 27-06-2020, 19:36   #5
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Re: Cork Gasket for Diesel Tank Inspection Port?

After looking a bit more into it, it seems cork with Buta-N is widely used, with pure Buta-N gasket material being even better. I got a sheet of it from McMasterCarr. As I understand it, pure Buta-N isn't going to degrade over time, unlike the cork.
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Old 28-06-2020, 16:07   #6
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Re: Cork Gasket for Diesel Tank Inspection Port?

Quote:
Originally Posted by aybabtme View Post
After looking a bit more into it, it seems cork with Buta-N is widely used, with pure Buta-N gasket material being even better. I got a sheet of it from McMasterCarr. As I understand it, pure Buta-N isn't going to degrade over time, unlike the cork.
Thanks for posting back with your choice, good to learn alternatives.Are you going to use it with or without sealant?
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Old 28-06-2020, 16:17   #7
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Re: Cork Gasket for Diesel Tank Inspection Port?

Rubber impregnated cork is great for diesel tanks. or maybe it's actually nitrile or Buna-n rubber impregnated cork. I know gaskets without cork in them tend to squeeze out when you tighten.
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Old 29-06-2020, 07:13   #8
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Re: Cork Gasket for Diesel Tank Inspection Port?

Quote:
Originally Posted by Compass790 View Post
Thanks for posting back with your choice, good to learn alternatives.Are you going to use it with or without sealant?
I put sealant on (Permatex Aviation #3), because the screws holding it together are going thru rather thin taped aluminum threads and thus can't get torqued too much.

Time will tell how well it works.
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Old 29-06-2020, 15:28   #9
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Re: Cork Gasket for Diesel Tank Inspection Port?

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Originally Posted by aybabtme View Post
I put sealant on (Permatex Aviation #3), because the screws holding it together are going thru rather thin taped aluminum threads and thus can't get torqued too much.

Time will tell how well it works.
Yea time is the test.
That 3 sealant is more for machined faces, I suspect Permatex 85420 would be better for your job but the No.3 should still work anyway.
Wise decision to use sealant if there are no nuts on the inside. Hope you put sealant on the screws as well.
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Old 29-06-2020, 18:08   #10
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Re: Cork Gasket for Diesel Tank Inspection Port?

I honestly don't know anything about the seemingly endless types of gasket material from Permatex, I just went with what was recommended around here in other threads.

What's the difference, and is there a set of such products I should familiarize myself with?
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Old 29-06-2020, 20:54   #11
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Re: Cork Gasket for Diesel Tank Inspection Port?

Sorry for worrying you. Pretty sure you'll be fine as the gasket material would probably be ok by itself except for maybe the screws. Its best to look at the Permatex website for the application they recommend. If it says for machined faces that means it wont be able to fill as big a gap as the 85420 which you can use without a gasket even.
I should have said nothing except about putting it on the screws as well. As you say other people have used No. 3 successfully & I'm sure you'll be fine with it too
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