Removing wingtop sight fuel indicators.

[0TreeLemur]

Recently bought replacement wingtop sight fuel level indicators.  I've read that they are held in their socket by silicone.   How does one go about removing them without damaging the socket?    Is there a snap ring around the top?  Thx.  -Fred

[N201MKTurbo]

Nothing holds them in but the silicone. I usually use a small screwdriver. If you are replacing them, you can be pretty violent to the capsule. The part attached to the airplane is pretty stout, so I wouldn’t worry about it too much.

I would mask the wing with a couple of layers of tape to keep from scratching it if you slip. I would start by prying up on the locating tab.

[PT20J]

Might also try heating with a heat gun to soften the RTV.

[0TreeLemur]

Done.  Here are the steps I took on the second one, because I learned a bit from the first one.  Here's a HOWTO in the style of @carusoam, with supporting photos.

1. Tools: carpet knife, two thin flat blade screwdrivers, plastic scraper

2. Target: crazed sight gage lens

3.  Score lens with knife until through

4. Insert small blade screwdriver through plastic lens where scored through

5. Gently pry to break out lens in chunks

6. Insert small screwdriver around perimeter and gently pry up

7. Once you get it up far enough to insert a second screwdriver, pry sequentially to extend gap

8. At some point you'll hear the silicone bonds start to break

9. Lift old gauge out

10. Bottom of gage receptacle is full of dried silicone

11. Use plastic scraper to remove

12. It takes some elbow grease

13. Viola!

 

 

 

[N201MKTurbo]

33 minutes ago, 0TreeLemur said:

Done.  Here are the steps I took on the second one, because I learned a bit from the first one.  Here's a HOWTO in the style of @carusoam, with supporting photos.

1. Tools: carpet knife, two thin flat blade screwdrivers, plastic scraper, pliers

2. Target: crazed sight gage lens

3.  Score lens with knife until through

4. Insert small blade screwdriver through plastic lens where scored through

5. Gently pry to break out lens in chunks

6. Insert small screwdriver around perimeter and gently pry up

7. Once you get it up far enough to insert a second screwdriver, pry sequentially to extend gap

8. At some point you'll hear the silicone bonds start to break

9. Lift old gauge out

10. Bottom of gage receptacle is full of dried silicone

11. Use plastic scraper to remove

12. It takes some elbow grease

13. Viola!

 

 

 

Nice job! I knew you would figure it out!

[Fredrik Andersson]

How did you put the new one in? With silicone? One of mine popped out accidentally above FL200. I heard a soft “cling” and took a while before I realized what it was…

[carusoam]

Welcome aboard Fredrik!
 

Silicone and painters tape…

Best regards,

-a-

10 minutes ago, Fredrik Andersson said:

How did you put the new one in? With silicone? One of mine popped out accidentally above FL200. I heard a soft “cling” and took a while before I realized what it was…

 

[carusoam]

If only there was an FAQ section….

This would be a perfect entry for it….  

Best regards,

-a-

[0TreeLemur]

3 hours ago, Fredrik Andersson said:

How did you put the new one in? With silicone? One of mine popped out accidentally above FL200. I heard a soft “cling” and took a while before I realized what it was…

Yes,  silicone.   As you can see, the person who installed the ones that I removed used too much.  They almost filled the receptacle, and most of it was not in contact with the indicator capsule.   I tried not to use too much.  Just put a small bead around the outer edge of the capsule that makes contact with the recessed rim and install it.   I used painters tape on the face of the dial so I could insert it without having to hold it by the edges.

[1980Mooney]

14 hours ago, Fredrik Andersson said:

How did you put the new one in? With silicone? One of mine popped out accidentally above FL200. I heard a soft “cling” and took a while before I realized what it was…

 

11 hours ago, 0TreeLemur said:

Yes,  silicone.   As you can see, the person who installed the ones that I removed used too much.  They almost filled the receptacle, and most of it was not in contact with the indicator capsule.   I tried not to use too much.  Just put a small bead around the outer edge of the capsule that makes contact with the recessed rim and install it.   I used painters tape on the face of the dial so I could insert it without having to hold it by the edges.

Actually I disagree.  They didn't use enough.  The receptacle should be filled.  If you try to "not use too much" you may create a void along the circumference of the gauge or a weak spot that creates a void over time.  You run the risk that water will find a way over time into the open area behind the gauge.  The first time you experience freezing temperatures on the ground or at high altitudes the water will freeze, expand and loosen/pop the disc gauge out.  It does not matter if RTV (silicone) is in contact with the back of the disc gauge.  It works magnetically.  

I recently replaced a gauge because the A&P shop damaged the face.  The gauge was originally installed by Lone Star Aero (San Antonio) in 2001.  Lone Star was a long time Mooney specialist shop.  The void was completely filled with RTV (silicone).  

I did the same when installing (after cleaning out all the old RTV (silicone)). Remember that RTV (silicone) needs to be exposed to humid air for a certain amount of time before the cross-linking can occur.  So don't just squeeze the RTV (silicone) in and press it together - it may not set up for a long, long time. (it's like putting the cap on an open tube - the tube may stay soft for a long time).  Follow the manufacturer instructions - usually you press together and pull apart exposing to air for about 5 minutes.  Then press together the final time.  It depends upon the product, humidity and temperature.  

Edited May 17, 2023 by 1980Mooney

[N201MKTurbo]

1 hour ago, 1980Mooney said:

 

Actually I disagree.  They didn't use enough.  The receptacle should be filled.  If you try to "not use too much" you may create a void along the circumference of the gauge or a weak spot that creates a void over time.  You run the risk that water will find a way over time into the open area behind the gauge.  The first time you experience freezing temperatures on the ground or at high altitudes the water will freeze, expand and loosen/pop the disc gauge out.  It does not matter if RTV (silicone) is in contact with the back of the disc gauge.  It works magnetically.  

I recently replaced a gauge because the A&P shop damaged the face.  The gauge was originally installed by Lone Star Aero (San Antonio) in 2001.  Lone Star was a long time Mooney specialist shop.  The void was completely filled with RTV (silicone).  

I did the same when installing (after cleaning out all the old RTV (silicone)). Remember that RTV (silicone) needs to be exposed to humid air for a certain amount of time before the cross-linking can occur.  So don't just squeeze the RTV (silicone) in and press it together - it may not set up for a long, long time. (it's like putting the cap on an open tube - the tube may stay soft for a long time).  Follow the manufacturer instructions - usually you press together and pull apart exposing to air for about 5 minutes.  Then press together the final time.  It depends upon the product, humidity and temperature.  

Exactly!

I would just add to smear some on the back of the capsule so you get good adhesion. It needs to extrude silicone all the way around when you push it in. If you wait overnight then peel off the extrusion, the cleanup is easy. I’ve never had any issues with it curing.

[mooniac15u]

On 5/1/2023 at 7:27 PM, 0TreeLemur said:

Recently bought replacement wingtop sight fuel level indicators.  I've read that they are held in their socket by silicone.   How does one go about removing them without damaging the socket?    Is there a snap ring around the top?  Thx.  -Fred

Where did you find the new ones?

[1980Mooney]

2 minutes ago, mooniac15u said:

Where did you find the new ones?

Don Maxwell has them in stock.  

[0TreeLemur]

On 5/17/2023 at 12:19 PM, 1980Mooney said:

 

Actually I disagree.  They didn't use enough.

Evidence suggests otherwise.   Even without adhesion on the bottom of the capsule, those have stayed in my J for years (decades?).   There isn't one "right" way to do this.

[Bolter]

In household projects, I have weakened RTV with vinegar.  Does not dissolve it magically, but makes it weaker.  Applying that could help with a strong fit during the prying phase.  -dan 

[Ryan ORL]

Looking at these photos makes me confused about how these things work... I expected some sort of wire or mechanical linkage in the back, but there appears to be nothing?

Anyway, my sight gauge glass is all fogged up so I'd like to replace mine also.  Glad to hear they're still available.

[PT20J]

15 minutes ago, Ryan ORL said:

Looking at these photos makes me confused about how these things work... I expected some sort of wire or mechanical linkage in the back, but there appears to be nothing?

Anyway, my sight gauge glass is all fogged up so I'd like to replace mine also.  Glad to hear they're still available.

The connection to the tank float is magnetic.

[Fredrik Andersson]

My indikator that suddenly popped out at FL220 is now replaced. It was in rain several days when attending the Friedrichshafen aero and then at the flight home, at freezing flight levels, made it pop out. I used white Marine silicon valid for -60° to 180°C, filled it completely after had removed the old silicone that was still there. Then the day after I put a film of 3M (used to protect the wing front) over complete installation so now it will never plop out again and no humid will get in. I cover the other with a film directly when first plopped out and it works well. If there are some mist inside the indicator, it goes away after few days in a dry hangar. It went little misty when I covered the old one, but it is gone away completely now.

[Fly Boomer]

5 hours ago, Fredrik Andersson said:

My indikator that suddenly popped out at FL220 is now replaced. It was in rain several days when attending the Friedrichshafen aero and then at the flight home, at freezing flight levels, made it pop out. I used white Marine silicon valid for -60° to 180°C, filled it completely after had removed the old silicone that was still there. Then the day after I put a film of 3M (used to protect the wing front) over complete installation so now it will never plop out again and no humid will get in. I cover the other with a film directly when first plopped out and it works well. If there are some mist inside the indicator, it goes away after few days in a dry hangar. It went little misty when I covered the old one, but it is gone away completely now.

The 3M product is a clear tape?

[Fredrik Andersson]

On 5/20/2023 at 2:11 AM, Fly Boomer said:

The 3M product is a clear tape?

Yes!

Edited July 4, 2023 by Fredrik Andersson