Jump to content

Maxwell tank leak detection experience


RobertGary1

Recommended Posts

On December 23, 2016 at 1:32 PM, Piloto said:

To prevent future leaks in the leak vicinity I recoat the whole tank cell instead of just spot resealing.

José

 

How much sealant is typically required to spot patch and then reseal all joints? Is one sealant better or easier to use?

Link to comment
Share on other sites

I just patched my right tank using the Maxwell method.  Tonight I replaced the drain and put about 1/2 tank of gas to check for leaks before replacing the access cover.   So far so good.  Do I need to drain the gas back out before replacing the access cover?  My A&P said not but I wanted to see what others had to say.  My question is will the access cover sealant cure ok with gas in the tank?  Thanks

Link to comment
Share on other sites

1 hour ago, Hyett6420 said:

It gets to the point though that you csnt keep doing that and you start getting corrosion under the patches etc.   Before they patch make sure there is no corrosion under the existing sealant or you are just saving up a huge bill for later.  

Oh sure. I was responding to the suggestion that a reseal was an alternate to weap repair. For  now a few bucks in sealant and an afternoon is a pretty low cost  

-Robert 

Edited by RobertGary1
Link to comment
Share on other sites

Thanks for all the great info. I'd never heard of the fill the tank with water method. It sounds like a bigger hassle although honestly I can't think of why. Maybe it seems wrong to fill your fuel tank with water but logically I think i'm going to talk myself into it. It does seem like it would work better than soapy bubbles.

 

-Robert

Link to comment
Share on other sites

On 12/25/2016 at 3:59 PM, Wakeup said:

Looks like mine are leaking at the top after topping off the tanks.  It started after first freeze.   When they resealed  last month /(year) they repainted the top and looks great.  Question ?..Can my guy go from the bottom and fix it so we don't have to damage the top panel ?  I'm so tired of dealing with my tanks.  I will only buy a Mooney with bladders next time.   I actually bought a Cherokee Six last week but would like to keep the Mooney too.  

The bottom are usually seal with regular permanent sealant. MIght be hard to remove them. The top are sealed with access panels sealant which is designed to be removed. But if it only leaks at the top then its only a brief problem between the time you fuel and you burn it down? :)

 

-Robert

 

Link to comment
Share on other sites

Robert,

  Not sure this will make you feel any better but if I'm not mistaken, DMax uses water to wash out all of the soapy bubbles after his check method, using water to completely fill the tank and rinsing the soap out.  I have recently used the just fill the tank with water method and it works great.  Just be sure to cap off the fuel line using the splice at the wing root in the cabin.  I fabricated two plexi-glass plates to tape over the access panel holes, dropped a mirror on each side of the rib I was checking and applied a slight vacuum to the fuel tank vent tube, found three leaks in a matter of 2 minutes. Drained the water through the sump drain, patched the leaks, let the sealant cure, refilled the tanks with water to check my work and viola!  No more leaks, no soap to clean up, and now we just re-attach the fuel line splice, fill the tanks with fuel, let sit for a couple of days before sign-off.

 

Hope this helps,

Ron

  • Like 1
Link to comment
Share on other sites

14 minutes ago, Marcopolo said:

Robert,

...  No more leaks, no soap to clean up, and now we just re-attach the fuel line splice, fill the tanks with fuel, let sit for a couple of days before sign-off.

 

Hope this helps,

Ron

Thank you! Just curious why you need to splice the fuel line vs just closing the fuel selector. Are you worried about water displacing the fuel in the line?

 

-Robert

Link to comment
Share on other sites

I felt it better to limit the travel of the water to the splice, if I were to leave the splice in place and use the fuel shutoff as my gate to keep the water on the left side only, I would have to make sure not to move the selector and to completely drain the line of water prior to starting the engine.  I just felt that using the fuel selector allowed the water a little too far down the line for my comfort and increased the possibility of other actions needed.  Just my opinion.

 

  I felt much the way you do as I stood there with a water hose filling a fuel tank, even more strange as I pulled the plane out of the hanger and let the water drain onto the ramp through the removed sump drain as people walked by with looks on their faces like...hmmmm... the FAA would love to see this.  We had drained the fuel into clean containers and allowed the tank to air dry for a good 24hrs before filling with water.

 

Ron

Link to comment
Share on other sites

36 minutes ago, Marcopolo said:

Robert,

  Not sure this will make you feel any better but if I'm not mistaken, DMax uses water to wash out all of the soapy bubbles after his check method, using water to completely fill the tank and rinsing the soap out.  I have recently used the just fill the tank with water method and it works great.  Just be sure to cap off the fuel line using the splice at the wing root in the cabin.  I fabricated two plexi-glass plates to tape over the access panel holes, dropped a mirror on each side of the rib I was checking and applied a slight vacuum to the fuel tank vent tube, found three leaks in a matter of 2 minutes. Drained the water through the sump drain, patched the leaks, let the sealant cure, refilled the tanks with water to check my work and viola!  No more leaks, no soap to clean up, and now we just re-attach the fuel line splice, fill the tanks with fuel, let sit for a couple of days before sign-off.

 

Hope this helps,

Ron

Sounds vaguely familiar, glad it worked.

Clarence

Link to comment
Share on other sites

  • 3 years later...
On 1/5/2017 at 10:13 PM, Marcopolo said:

Robert,

  Not sure this will make you feel any better but if I'm not mistaken, DMax uses water to wash out all of the soapy bubbles after his check method, using water to completely fill the tank and rinsing the soap out.  I have recently used the just fill the tank with water method and it works great.  Just be sure to cap off the fuel line using the splice at the wing root in the cabin.  I fabricated two plexi-glass plates to tape over the access panel holes, dropped a mirror on each side of the rib I was checking and applied a slight vacuum to the fuel tank vent tube, found three leaks in a matter of 2 minutes. Drained the water through the sump drain, patched the leaks, let the sealant cure, refilled the tanks with water to check my work and viola!  No more leaks, no soap to clean up, and now we just re-attach the fuel line splice, fill the tanks with fuel, let sit for a couple of days before sign-off.

 

Hope this helps,

Ron

Ron, I realize that this post is from yester-year, but was wondering if you have any photos from this project? I have slow, "tough to find" leaks in both wings and would like to use water method as well. However, I'm more of a visual person and struggling to visualize how to conduct a tank test with water...

Link to comment
Share on other sites

4 minutes ago, ukrsindicat@yahoo.com said:

I have been looking around, but it seems that D-MAX's "Fuel-Tank-Repair_How-We-Fix-Them" video has been deleted...

I copied it a while ago:

------------------------

Fuel Tank Repair - How We Fix Them 

 

         

 

Every week I receive several phone calls and e-mails regarding fuel tank leaks, with questions such as: 

 

“I smell fuel when I first get in the plane and then the smell goes away”; 

 

“I have a screw on the panel at the cabin door that leaks when the tank is full”;

 

“I have fuel stains in the wheel well”; 

 

“ I have a panel under the wing that leaks”; and

 

“ How much will it cost to have my tanks resealed?”

 

In most cases, the leak can be repaired and a total “strip and reseal” is not needed. We repair at least one fuel tank per week. 

 

Fuel smells in the Cabin

Your plane has been closed up for a period of time. You open the cabin door and smell fuel, and within a few minutes the smell is gone. 

 

The source of the fuel smell can be a fuel tank leak, a leaking fuel selector valve, or leaking fuel gauge sending unit. The leading edge of our Mooney wing is hollow. A fuel leak in the forward or outboard tanks will leak into the leading edge of the wing. The leading edge of the wing is open to the cabin at the forward edge of the seat track on each side of the cabin. Fuel fumes or smells enter the cabin at this point. Holes are drilled in the lower leading edge of the wing at each rib and at the fuselage. These holes are to prevent fuel from accumulating at the ribs and from entering the cabin. Fig. 1 is an example of the weep hole at the fuselage showing fuel leakage stains. 

 

Fuel Selector

Fuel selector valve leaks are evident by stains around the fuel selector stem. In most cases these leaks are repaired by disassembling the selector and replacing the O-rings.

 

Sending Units

Mooney M20 B thru E models have fuel gauge sending units located inside the cabin, just in front of the rear seats on each side of the cabin. Models F thru S have sending units in the same location, as well as, having an outboard sending unit in each wing. These sending units have cork or neoprene gaskets. Leaks in these areas will be detected by blue stains on the tank walls below the sending units. In most cases, tightening the screws that attach the sending unit will stop these leaks. 

 

Panel Screws

A leak found at a screw in an access panel is usually caused by a cracked nut plate. Fig. 2. The nut plate in the fuel tank has a plastic cap to keep the fuel from leaking around the screw threads. These caps, over time, become cracked due to age or possibly someone has replaced the screw with one that is too long. To repair the leak,remove the screw. You do not have to drain the tank. Apply a fuel resistant sealant, such as Permatex #3, to the screw threads and replace the screw in the panel.

The times I've done it I've taken the old screw out, cleaned the threads, put Permatex Aviation Sealant #3 (http://www.aircraftspruce.com/catalog/eppages/permatexprod4.php?clickkey=288791) on the new screw and reinstalled and it has worked very well every time. But those aren't my instructions I just followed Don's.

 

Fuel Tank Construction

A Mooney fuel tank is a metal box constructed out of several individual pieces. Once assembled, each seam is sealed with layers of a fuel resistant sealant. If this sealant is damaged by a hard landing, or by age, fuel can leak between the sealant and the tank walls, migrating to a point where it can exit. This point of exit may be a rivet or seam between wing skins. 

 

I have come across logbook entries where the same rivet has been replaced several times trying to stop a leak. Using our method, we have located the source of these leaks in other parts of the tank.

 

Finding Leaks

I did not invent this procedure, nor do I remember who told me; however, this is how our service center finds leaks in Mooney fuel tanks. 

 

1. The first rule to remember in chasing a fuel leak is: The source of the leak is never where the leak appears on the out side of the tank.

 

2. Remove the fuel from the tank. 

 

3. Turn the fuel selector off.

 

4. Remove the top fuel tank access panels on the wing that has the leak. The panels are removed by first removing the screws. 

 

5. Once the screws are removed, we use masking tape to tape around the access panel and the middle of the panel for protection of the paint. The panel is sealed with a sealant. Do not beat on the panels. An elephant could stand on the panel and it would not come loose.

 

6. Next, we use a thin putty knife, that has been sharpened on one side, to slide in between the seam of the access panel and the wing. Using a nonmetallic hammer, gently work the putty knife between the skin and panel. It may take several times around the panel with the blade and hammer, each round a little deeper under the skin, until the panel releases. 

 

7. Once the panels are removed we place mirrors in the bottom of the tank so that we will be able to see the upper seams of the tank. Do not cover the stringers in the bottom of the tank. Many leaks are in this area.

 

8. Next we apply liquid hand soap, thicker the better, to all the seams in the tank. 

 

9. We now cover all the removed access holes in the wing with Plexiglas. Fig. 3. The Plexiglas covers the entire hole including screw holes. The Plexiglas is held in place by masking or duct tape around the out side border forming a seal. The Plexiglas can be cut from an old windshield or purchased at most hardware stores. New glass is preferred as you will be looking thru the glass to find our leak source. 

 

10. Next we take a standard shop vacuum cleaner. We attach the hose from the vacuum cleaner to the vent on the fuel tank. And no, this will not collapse your tank. Fig. 4

 

 

11. Turn on the vacuum and, using a flashlight, look thru the Plexiglas panel and look for bubbles in the soap. The mirrors should be positioned so that you can see the entire interior of the tank.

 

12. Bubbles indicate the source of the leak as air is drawn into the tank thru the leak. 

 

13. Once the leak, or leaks, are found, Fig .5, the area will need to be thoroughly rinsed with water, dried, cleaned and repairs made using procedures in the Mooney Service Manual..

 

14. Two types of sealant are recommended in the manual. PRC and Flame Master brands. We use Flame Master CS3204B-2 for repairs in the tank and topped with CS-3600 for a protective coating and CS3330B-2 for access panel sealant. Fig 6. We use sealants in Semkits that contain both sealant & activators. They are mixed together in a small caulking tube. Once mixed together, we transfer the sealant to a cup and apply with small acid brushes. The sealant will apply easily if thinned with a small amount of MEK. 

 

15. Replace the access panels using CS3330B-2. I recommend at least 48 hours before fuel is added to allow for proper curing of the sealant. Temperature is key to a successful repair. Avoid cold weather & high humidity if possible. 

 

Most leaks are easily found and repaired using this method. I share this procedure with you so that you and your mechanic can locate and repair your Mooney’s fuel leak. We welcome you to visit our service center at any time.

-----------------

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

  • 2 weeks later...

Fantastic video UKRS...

Great example of the soap bubble test for Finding tank leaks!
 

Thanks for sharing the finding process...

Getting the soap out should take lots of water, sprayed in, and drained out... expect to find about a cup of water that is below the drain level.

PP thoughts only, not a mechanic...

 

Best regards,

-a-

  • Like 1
Link to comment
Share on other sites

2 hours ago, ukrsindicat@yahoo.com said:

Since I'm visual person, I made videos of leak locations with my GoPro. Posted on youtube. 

Now the fun of removing all this soap from the tank. Any suggestions? I thought of water and shopvac.

I don’t have running water in my hangar, so I use a Hudson sprayer full of water and a shop vac.

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.