Leaky screw top of wing

[Danb]

Have a slight blue sighting on wing, what do you put on screw to stop leak

[Rwsavory]

Permatex No. 3

[Fritz1]

CS3204 tank sealant, clean treads with tap drill, will never leak again

[LANCECASPER]

  On 2/4/2024 at 8:55 PM, Danb said:

Have a slight blue sighting on wing, what do you put on screw to stop leak

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Yes they also call it Aviation Form-a-gasket. https://www.aircraftspruce.com/catalog/pnpages/09-28500.php

 

[Shadrach]

I’ve had pretty good luck with Hylomar Blue. Does not take much.

[jetdriven]

Use the right stuff. PR-1422

[Fly Boomer]

  On 2/4/2024 at 10:31 PM, jetdriven said:

Use the right stuff. PR-1422

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Flamemaster (Chemseal) CS-3204 is supposed to be the same as PPG (Proseal) PR-1422.
 

[Shadrach]

  On 2/4/2024 at 10:40 PM, Fly Boomer said:

Flamemaster (Chemseal) CS-3204 is supposed to be the same as PPG (Proseal) PR-1422.
 

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It is most certainly the same. After years of wet wing ownership, I personally prefer non-setting sealer where appropriate. These types of sealants tend to work pretty well on the top of the wing. I don’t like gluing screws in with 3204 unless I have no other option.

[Fly Boomer]

  On 2/4/2024 at 11:04 PM, Shadrach said:

It is most certainly the same. After years of wet wing ownership, I personally prefer non-setting sealer where appropriate. These types of sealants tend to work pretty well on the top of the wing. I don’t like gluing screws in with 3204 unless I have no other option.

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So, you are saying that you agree with @Fritz1 that CS-3204 is suitable for the job?

[Shadrach]

  On 2/4/2024 at 11:11 PM, Fly Boomer said:

So, you are saying that you agree with @Fritz1 that CS-3204 is suitable for the job?

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It will seal a leaking screw, so yes. However, suitable and ideal are not the same. Living with wet wings means having to open the tanks every now and again. I dislike the residual sealant that it leaves on the threads of the nut plate. If it were on the underside of the wing, I would use CS3330 access door sealant  it is “non adhesive” and easier to remove.

[PT20J]

The truth is -- any thread sealant that is impervious to gasoline will work. I know a mechanic that likes to make sure he can get the screw out again and he uses EZ-Turn. It works. I prefer Permatex 2 -- it's a thicker than 3, but there are lots of choices. CS-3204 seems overkill for a screw, but it's probably what the factory would recommend.

[jetdriven]

  On 2/4/2024 at 10:40 PM, Fly Boomer said:

Flamemaster (Chemseal) CS-3204 is supposed to be the same as PPG (Proseal) PR-1422.
 

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it is. 

[jetdriven]

  On 2/5/2024 at 12:23 AM, PT20J said:

The truth is -- any thread sealant that is impervious to gasoline will work. I know a mechanic that likes to make sure he can get the screw out again and he uses EZ-Turn. It works. I prefer Permatex 2 -- it's a thicker than 3, but there are lots of choices. CS-3204 seems overkill for a screw, but it's probably what the factory would recommend.

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The reason the screw is leaking because either the sealant over the open end of the nut plate is compromised or fuel is seeping in from the edges of panel to the shank of the screw but either way those are both also polysulfide sealants.  The panel is held in with CS3330 and the nutplate I think is sealed with PR1422/CS3204.

[PT20J]

  On 2/5/2024 at 1:13 AM, jetdriven said:

The reason the screw is leaking because either the sealant over the open end of the nut plate is compromised or fuel is seeping in from the edges of panel to the shank of the screw but either way those are both also polysulfide sealants.  The panel is held in with CS3330 and the nutplate I think is sealed with PR1422/CS3204.

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I'm not disagreeing with you, but the nutplate is a sealed type and sometimes the reason it leaks is that someone put in too long a screw. I would try something simple first since it's not a safety of flight issue and if it doesn't work, I could always do something else. I understand that a shop would want to use a method guaranteed to avoid the airplane returning for the same problem.

[Shadrach]

  On 2/5/2024 at 1:48 AM, PT20J said:

I'm not disagreeing with you, but the nutplate is a sealed type and sometimes the reason it leaks is that someone put in too long a screw. I would try something simple first since it's not a safety of flight issue and if it doesn't work, I could always do something else. I understand that a shop would want to use a method guaranteed to avoid the airplane returning for the same problem.

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Or sometimes someone tried to stop a leak by putting too much 3330 or 3204 in the screw hole and then when the screw was tightened it pushed the sealed caps off the back of the nut plate. I’ve opened tanks and seen sealant stalagmites and stalactites where sealant was pushed through the nut plates.

[Shadrach]

  On 2/5/2024 at 1:13 AM, jetdriven said:

The reason the screw is leaking because either the sealant over the open end of the nut plate is compromised or fuel is seeping in from the edges of panel to the shank of the screw but either way those are both also polysulfide sealants.  The panel is held in with CS3330 and the nutplate I think is sealed with PR1422/CS3204.

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On the vintage birds at least, the nut plate is sealed with a fuel proof cap during manufacture. It’s not hard to push them off the nut plate by pressurizing the screw hole with 3330 or 3204. The sealant will squeeze out around the cap like grease around a bushing. It will then leak for sure until the nut plate is replaced or resealed with with 3204 from the backside.

 

[LANCECASPER]

A light coat of Permatex #3 on the bottom part of the threads of the screw has worked for me on two different Mooneys. When you screw it in the permatex gets distributed on the entire screw. Obviously the fuel level has to be lower than the bottom the screw. I used a new equivalent screw both times so I didn't have any old sealant to deal with on the screw. It does take awhile for the Permatex to set up - I let it cure for 24 hours before I put a new wing walk on that area. This recommendation came from a Don Maxwell article years ago and works well. He continues to mention this method at seminars and  his shop still seals top side screws that way.

[Shadrach]

  On 2/5/2024 at 1:58 PM, LANCECASPER said:

A light coat of Permatex #3 on the bottom part of the threads of the screw has worked for me on two different Mooneys. When you screw it in the permatex gets distributed on the entire screw. Obviously the fuel level has to be lower than the bottom the screw. I used a new equivalent screw both times so I didn't have any old sealant to deal with on the screw. It does take awhile for the Permatex to set up - I let it cure for 24 hours before I put a new wing walk on that area. This recommendation came from a Don Maxwell article years ago and works well. He continues to mention this method at seminars and  his shop still seals top side screws that way.

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The only thing I would add to this is that in addition to using a new screw, it would also be a good idea to gently clean the nut plate threads of old sealant. Cautious use of a thread chaser and compressed air is usually sufficient.

[PT20J]

I used the sealant technique on two screws on bottom plates that had slight evidence of staining and it has held. I also used it on CiES fuel sender screws. 3 out of 4 senders developed seepage at one or two screws each.

[Danb]

The slight leak is not under the wing walk but the plate just to the right of it. 

[LANCECASPER]

  On 2/5/2024 at 4:58 PM, Danb said:

The slight leak is not under the wing walk but the plate just to the right of it. 

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Is it a rivet or screw? I have a slight seep on a rivet  just off to the side of the wing walk if it's filled to the max. The paint is blue so it doesn't botehr me too much.

[Shadrach]

  On 2/5/2024 at 4:58 PM, Danb said:

The slight leak is not under the wing walk but the plate just to the right of it. 

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It does not really matter whether it’s under the wing walk or not. Those screws are just as easily removed and reinstalled. Whatever the sealant that you decide use, be mindful to use just enough to seal the threads and screw head.

[Bartman]

I had this problem a couple of years after a complete reseal.  Remove the screw and install a new one.  I applied Permatex #3 to the last couple of threads closest to the beveled area of the screw and some on the bevel itself.  

No runs, no drips, no errors.