Maxwell tank leak detection experience

[RobertGary1]

I'd like to hear from those who have used Maxwell's technique of detecting fuel tank leaks. Specifically..

1) What type of soap did you use? It seems like you'd need something heavy that won't run off.

2) How did you put the plastic over the inspection panels? Maybe just slather petroleum jelly and set it over the panel?

3) How did you seal the vacuum attachment around the filler?

 

I've always had success with a casual application of sealant in the general area of a fuel stain every few years. But I'd like to give Don's method a try.

-Robert

[DonMuncy]

Try http://donmaxwell.com/publications/MAPA_TEXT/_overlay/Fuel Tank Repair_How We Fix Them 2-05.htm

[RobertGary1]

4 minutes ago, DonMuncy said:

Try http://donmaxwell.com/publications/MAPA_TEXT/_overlay/Fuel Tank Repair_How We Fix Them 2-05.htm

That's what I already have. But it doesn't answer the questions.

[DonMuncy]

I'm sorry. I thought he gave the details, although I did not read it carefully this time..

[lamont337]

2 hours ago, RobertGary1 said:

I'd like to hear from those who have used Maxwell's technique of detecting fuel tank leaks. Specifically..

1) What type of soap did you use? It seems like you'd need something heavy that won't run off.

2) How did you put the plastic over the inspection panels? Maybe just slather petroleum jelly and set it over the panel?

3) How did you seal the vacuum attachment around the filler?

 

I've always had success with a casual application of sealant in the general area of a fuel stain every few years. But I'd like to give Don's method a try.

-Robert

1) Dish soap. Doesn't really need to be thick, it's the suds that you need. 

2) Duct tape at first. It left some residue so I switched to some wide painters tape. Worked just as well. 

3) Didn't. As that panel with the filler cap  was removed in place of plexi I held the vacuum up to the vent on the bottom of the wing. I found that if I tilted the hose so that it wasn't completely flush with the skin it still provided enough suction to bend the plexi inward. The vent on my C is most likely different from your F. In fact my fuel cap is under an access panel with a scupper so there will of course be differences.

The last time I did this I didn't even bother with soap. There was about 8 gallons of fuel remaining so I just put the plexi in place and applied suction. The bubbles were very easy to see coming up through the fuel and causing ripples at the surface. Good lighting is important. Tossing a few glow sticks under the plexi would sure help. Good luck.  

 

 

[Guest]

The problem I've found is too many bubbles.  I recently helped an owner with his tanks.  After taping clear plexiglass covers on top of the wings we filled the tanks with water then connected a shop vacuum to a hole drilled in one of the plexiglass covers.  Air bubbles were easy to spot with no foaming.

Clarence

[Yetti]

Not sure I would want gasoline fumes being sucked into a spinning electric motor

[RobertGary1]

2 hours ago, Yetti said:

Not sure I would want gasoline fumes being sucked into a spinning electric motor

There isn't supposed to be fuel in the tank. I guess there could be some small amount of vapor 

-Robert

[Guest]

7 hours ago, Yetti said:

Not sure I would want gasoline fumes being sucked into a spinning electric motor

Where would gasoline fumes come from?  All of the upper covers have been removed and the tank drained and cleaned prior to pulling vacuum on the tank.

Clarence

[Yetti]

13 hours ago, lamont337 said:

The last time I did this I didn't even bother with soap. There was about 8 gallons of fuel remaining so I just put the plexi in place and applied suction. The bubbles were very easy to see coming up through the fuel and causing ripples at the surface. Good lighting is important. Tossing a few glow sticks under the plexi would sure help. Good luck.  \

 

[nels]

What is the best way to get the inspection covers off? I assume a thin putty knife, plenty of time and gentle working of the knife or is there a trick I don't know? Do you typically just remove the top covers?

[Piloto]

I use a simpler blow job procedure:

1. Defuel the tank completely through the drain valve. Replace valve after empty tank 

2. Set fuel selector to the opposite tank.

3. Attach a hose to the vent. Seal the coaxial tubing for models M20J and before.

4. Secure fuel cap.

5. Spray foamy soap cleaner like SD-20 around the suspected area next to the tank structure.

6. Blow by mouth only into the vent hose. This avoids skin stressing since your lungs will break before too much pressure.

7. Watch for bubbles in the suspected area.

Total tank integrity can be check by bending the hose with air pressure in the tank and after half hour checking for air pressure still in the tank.

Using an altimeter pressure to -1000ft. Because of the warm  air coming from your lungs the pressure will drop initially about 200ft and then stabilize. I have seen tanks holding pressure for over two hours.

Once you have located the suspected area open the tank cover next to the leak. For pinpoint location on the inside blow compressor air inside the tank into the suspected area with an air nozzle until bubbles are seen outside.

The above is also useful to check for fuel cap leaks on the O-ring and on the adapter. 

I would not vacuum the tank since it can pull sealant from the structure.

José

 

[RobertGary1]

1 hour ago, nels said:

What is the best way to get the inspection covers off? I assume a thin putty knife, plenty of time and gentle working of the knife or is there a trick I don't know? Do you typically just remove the top covers?

Yes. Plastic putty knife though. Work slowly to de-bond it to avoid bending inspection plate.  When installing be uber careful to not get sealant into the nut holes or they'll pop off. Not a problem at the time but will fall away next time you go in. 

-Robert

[nels]

18 minutes ago, RobertGary1 said:

Yes. Plastic putty knife though. Work slowly to de-bond it to avoid bending inspection plate.  When installing be uber careful to not get sealant into the nut holes or they'll pop off. Not a problem at the time but will fall away next time you go in. 

-Robert

Do you mean keep the sealant out of the threads?

[C-GHIJ]

There is a better way to do it.  (Thanks Clarence, I'm the owner he helped).  

1.  Drain the tank completely, and open up the top access covers and clean out the tank.

2.  Cover or plug the fuel intake pipe.

3.  Cover or plug vent line from the outside.

4.  Fill tank with water.

5.  Cover the tank openings with clear plexiglas and seal with tape. One piece will need to have a hole in it the size of a shop vac hose.

6.  Apply vacuum and watch the bubbles appear.  Very easy to see through the plexiglas.

7.  Drain and dry tank well before you repair.

Easy as pie.  Worked great.  Thanks again Clarence, you are a wealth of knowledge.  

[Piloto]

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

José

 

[bonal]

Tiny bubbles, that would make an interesting video to help learn what to look for

[N201MKTurbo]

On 12/22/2016 at 6:15 PM, nels said:

What is the best way to get the inspection covers off? I assume a thin putty knife, plenty of time and gentle working of the knife or is there a trick I don't know? Do you typically just remove the top covers?

This is the perfect tool:

http://www.aircraft-tool.com/shop/detail.aspx?PRODUCT_ID=SWG7

It will get under the edge without maring the panel or the wing.

[nels]

29 minutes ago, N201MKTurbo said:

This is the perfect tool:

http://www.aircraft-tool.com/shop/detail.aspx?PRODUCT_ID=SWG7

It will get under the edge without maring the panel or the wing.

Thanks, I think I'll buy one. Do they last or should I buy two as an insurance policy?

[N201MKTurbo]

41 minutes ago, nels said:

Thanks, I think I'll buy one. Do they last or should I buy two as an insurance policy?

It'll last forever.

[DonMuncy]

That doesn't mean you won't lose it in 3 days.

[nels]

7 hours ago, DonMuncy said:

That doesn't mean you won't lose it in 3 days.

Haha. How true that is!!

[N131MA]

One more option for finding the leak is gas leak detection spray like the example below.

The bubbles are very easy to see and the leak finder can be washed out with some 100ll after locating the leaks.

https://www.amazon.com/Nu-Calgon-4182-24-Detector-Bottle-1-Quart/dp/B000R7Z6L4/ref=sr_1_1?ie=UTF8&qid=1482614362&sr=8-1&keywords=leak+detection+spray

[bradp]

Perfect tool is in fact perfect.  I've used it for so many other projects.  

[Wakeup]

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.