Best Way To Seal Fuel Tank Opening

[Gary Lewis]

I'm having to replace the o-ring on the midship tank on Big Blue as it leaks. Again. I replaced it about 2 years ago, but apparently didn't do a perfect job, so now I'm wondering what is the best way to seal the o-ring? And the o-ring is the one under the lock ring, as shown below.

So is there a sealant, like maybe Permatex Permashield, that will hold the o-ring in place for assembly awa seal it? I'd rather not do this again.

[Rusty_S85]

I'm having to replace the o-ring on the midship tank on Big Blue as it leaks. Again. I replaced it about 2 years ago, but apparently didn't do a perfect job, so now I'm wondering what is the best way to seal the o-ring? And the o-ring is the one under the lock ring, as shown below.

So is there a sealant, like maybe Permatex Permashield, that will hold the o-ring in place for assembly awa seal it? I'd rather not do this again.

https://forum.garysgaragemahal.com/file/n126964/61nOSgeBlIL.jpg

How tight does the ring fit? Ive had to take a hammer and a screw driver to the tank and ding the ears down to hold the plate tighter before. If the fit is good and the O ring is simply popping out of the groove, you could try some fuel safe gasket adhesive to stick the O ring into the groove and keep it form possibly moving.

[Gary Lewis]

I'm having to replace the o-ring on the midship tank on Big Blue as it leaks. Again. I replaced it about 2 years ago, but apparently didn't do a perfect job, so now I'm wondering what is the best way to seal the o-ring? And the o-ring is the one under the lock ring, as shown below.

So is there a sealant, like maybe Permatex Permashield, that will hold the o-ring in place for assembly awa seal it? I'd rather not do this again.

https://forum.garysgaragemahal.com/file/n126964/61nOSgeBlIL.jpg

How tight does the ring fit? Ive had to take a hammer and a screw driver to the tank and ding the ears down to hold the plate tighter before. If the fit is good and the O ring is simply popping out of the groove, you could try some fuel safe gasket adhesive to stick the O ring into the groove and keep it form possibly moving.

The existing ring fit tightly when I put it on, although I haven't tested it lately. But I'd bet it is still quite tight.

But we are thinking alike - the o-ring may be popping out of the groove. And that Permatex is "fuel resistant" so should work.

However, it is also sticky and I'm wondering if it might cause the o-ring to try to follow the lock ring on the top side and be stuck on the bottom if I put it all over the o-ring. So maybe goo the tank and lay the o-ring in it then oil the lock ring and put it on?

Or, I've thought about using Loctite PTFE goo instead of the Permatex. The writeup on it says "Loctite 567 seals threaded pipe and fittings instantly, then slowly hard-cures to form an insoluble seal which exceeds the pressure rating of all sized pipes. Lubricates threads during assembly and permits accurate positioning of elbow, valve and gauges before setting. Excellent chemical resistance. Temp. range: -65F to 400F (-54C to 204C)."

[grumpin]

The existing ring fit tightly when I put it on, although I haven't tested it lately. But I'd bet it is still quite tight.

But we are thinking alike - the o-ring may be popping out of the groove. And that Permatex is "fuel resistant" so should work.

However, it is also sticky and I'm wondering if it might cause the o-ring to try to follow the lock ring on the top side and be stuck on the bottom if I put it all over the o-ring. So maybe goo the tank and lay the o-ring in it then oil the lock ring and put it on?

Or, I've thought about using Loctite PTFE goo instead of the Permatex. The writeup on it says "Loctite 567 seals threaded pipe and fittings instantly, then slowly hard-cures to form an insoluble seal which exceeds the pressure rating of all sized pipes. Lubricates threads during assembly and permits accurate positioning of elbow, valve and gauges before setting. Excellent chemical resistance. Temp. range: -65F to 400F (-54C to 204C)."

I used Dow Corning 4 on o rings on aircraft. A dielectric compound. That stuff is kind of spendy.

Silicone is good to use, keeps the o ring in place to do it’s job.

[Gary Lewis]

I used Dow Corning 4 on o rings on aircraft. A dielectric compound. That stuff is kind of spendy.

Silicone is good to use, keeps the o ring in place to do it’s job.

Dane - I just happen to have Dow Corning 4, which I use to fill cable connectors before inserting the wire and crimping them to make sure nothing else gets in.

So you are saying to coat the o-ring w/it and lay it on the tank, put the clamp ring on it, and tighten it up? Nothing more?

It is sticky enough that the o-ring won't jump out of the depression it fits in and yet it is slick enough to let the lock ring slide?

How 'bout a deviation: I coat the tank's groove with the Permatex and lay the ring in it and let that set up a bit. Then coat the clamp ring with the silicon and put it in place. Might that give me a better chance for the o-ring to stay put?

[Rusty_S85]

The existing ring fit tightly when I put it on, although I haven't tested it lately. But I'd bet it is still quite tight.

But we are thinking alike - the o-ring may be popping out of the groove. And that Permatex is "fuel resistant" so should work.

However, it is also sticky and I'm wondering if it might cause the o-ring to try to follow the lock ring on the top side and be stuck on the bottom if I put it all over the o-ring. So maybe goo the tank and lay the o-ring in it then oil the lock ring and put it on?

Or, I've thought about using Loctite PTFE goo instead of the Permatex. The writeup on it says "Loctite 567 seals threaded pipe and fittings instantly, then slowly hard-cures to form an insoluble seal which exceeds the pressure rating of all sized pipes. Lubricates threads during assembly and permits accurate positioning of elbow, valve and gauges before setting. Excellent chemical resistance. Temp. range: -65F to 400F (-54C to 204C)."

I would only apply it to the tank side and just enough to lock the o ring in place. Dont put too much as it will make life hard if you ever have to clean the groove out down the road. This should prevent it from trying to stick to the lock ring as well.

[Gary Lewis]

I would only apply it to the tank side and just enough to lock the o ring in place. Dont put too much as it will make life hard if you ever have to clean the groove out down the road. This should prevent it from trying to stick to the lock ring as well.

Which "it"? Permatex or the PTFE? Permatex has to be cleaned out with brake cleaner, but the PTFE will wipe out fairly well.

[grumpin]

Dane - I just happen to have Dow Corning 4, which I use to fill cable connectors before inserting the wire and crimping them to make sure nothing else gets in.

So you are saying to coat the o-ring w/it and lay it on the tank, put the clamp ring on it, and tighten it up? Nothing more?

It is sticky enough that the o-ring won't jump out of the depression it fits in and yet it is slick enough to let the lock ring slide?

That’s what I would do. If it doesn’t work try your deviation method.

Here’s a picture of Pratt and Whitney PT6 turbine nozzles. 4 o rings per nozzle, 14 nozzles. I used to squirt a dollop of DC4 in my hand add the o rings and rub my hands together to get the DC4 on the orings.

[Gary Lewis]

Dane - I just happen to have Dow Corning 4, which I use to fill cable connectors before inserting the wire and crimping them to make sure nothing else gets in.

So you are saying to coat the o-ring w/it and lay it on the tank, put the clamp ring on it, and tighten it up? Nothing more?

It is sticky enough that the o-ring won't jump out of the depression it fits in and yet it is slick enough to let the lock ring slide?

That’s what I would do. If it doesn’t work try your deviation method.

Here’s a picture of Pratt and Whitney PT6 turbine nozzles. 4 o rings per nozzle, 14 nozzles. I used to squirt a dollop of DC4 in my hand add the o rings and rub my hands together to get the DC4 on the orings.

I don't like the "if it doesn't work" idea. This will be my third try and I want to ensure it does work.

I'm thinking about trying to seal the tank while I have it down and add 3 - 5 psi of air pressure to it and then spritz the area with a soap and water mix. Should be able to put air in via the vent, assuming the rollover valve doesn't pop out, plug the supply and return fittings, and hope the gas cap is truly sealed.

Thoughts?

[grumpin]

I don't like the "if it doesn't work" idea. This will be my third try and I want to ensure it does work.

I'm thinking about trying to seal the tank while I have it down and add 3 - 5 psi of air pressure to it and then spritz the area with a soap and water mix. Should be able to put air in via the vent, assuming the rollover valve doesn't pop out, plug the supply and return fittings, and hope the gas cap is truly sealed.

Thoughts?

Yes, I don’t blame you. I was assuming you could see the o ring if it popped out.

If you can get that pressure on it, I think that’s a good idea.