The place for technical discussions about GA and flying.
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jaycee58 wrote:I don't want to be overly pessimistic but surely a fuel tank drain shouldn't be that difficult to seal? I would examine the the thread in the tank drain very carefully for a very small crack axially along the thread or emanating radially from the drain.

We are talking two 'seals'.

Firstly with the existing drain in situ, one inserts the tester to take the sample, and on removing the tester we expect the spring loaded pin or whatever to close against the body of the drain thus sealing the orifice and stopping the fuel flow. Sadly this did not happen, so presumably a small flake of debris is preventing this.

I have learned over time that if a part is 20 + years old and gives a problem (and looks as though it has other flakes that could provide a repeat performance) it's better to just bite the bullet and buy a new replacement. £18c from Andair for a new stainless steel one with viton seal (I assume for the spring loaded pin!).

The second seal is of course for the complete drain unit into the metal insert in the fibreglass fuel tank, for which as it seems crush washers are not used, some sort of goo is required, that Trent has very kindly sent me.

Of course it's possible that the pin did actually re-seal and something metallic fractured at the same time, but even I'm not that paranoid..........yet.
Curtiss valves are notorious for getting debris trapped in the little sealing O-ring and developing leaks. I used to carry a couple of spares all the time.

With practice, you can swap them without draining the tank. Seal the tank vent, keep the cap tight, have the new one prepared in your other hand and swap them quickly with barely a drop spilt. Don't forget to unblock the tank vent afterwards!

The most common sealant for NPT threads on fuel system components in the Permatex 567 (or Henkel/loctite equivalent) or EZ turn/Fuel Lube. EZ turn is great for the o-rings on flush fuel caps too.

You can just replace the seal o-ring on the Saf-air type curtiss valves.

I recently switched to the Andair version that has proven good so far.
User avatar
By Rob L
Charles Hunt wrote:Kindly supplied a small qty in plain packaging by Trent772, if he doesn't see this, drop him a pm.

Oh, and good luck - it'll be like chasing brake fluid around Morley!

Hey Charles, get Trent 722 to let us all in on his little secret; at least for those of us in the LAA fraternity that live "over here" rather than "over there". :wink:

I bet it's one of those already mentioned (or a chemical composition similar thereof).

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User avatar
By Rob L
Trent772 wrote:Nothing special, just EZ Turn fuel lube.

Be wary of searching on eBay..... :lol:

It is remarkably sticky, used on fuel lines and valves etc.

I wouldn't even THINK of buying what you suggest from Ebay, and I'd suggest you be careful of suggesting same, by the use of your smilie.

My opinion of you has diminished somewhat.

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