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Leaky fuel tank woes ... looking for perspectives


Immelman

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Don Maxwell just resealed one of my tanks.

He noticed a leak in the left tank during the annual after my purchase and when he went in to take a look he found two or three metal tools/scrapers that were left inside the tank during a previous service.  They were rusted and no doubt creating quite a few problems during their time there.  Glad to have the new seal in place.

 

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Don Maxwell just resealed one of my tanks.
He noticed a leak in the left tank during the annual after my purchase and when he went in to take a look he found two or three metal tools/scrapers that were left inside the tank during a previous service.  They were rusted and no doubt creating quite a few problems during their time there.  Glad to have the new seal in place.
 

What did Maxwell charge for the reseal?


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I would surmise that if a low vacuum caused a leak that it would just be an alert to weak sealant that was going to be the next area to patch.

(Boy, am I ever glad that my '66E has 64 gallon bladders! A 50 year old plane has enough other systems to be vigilant about...) 

@Immelman, you've had your plane for 10 years? And it's still worth $30k? and you haven't overhauled the engine, updated the panel, painted the plane, or replaced the interior? ISTM that she's treated you pretty darn well, and it's Valentine's Day, do something nice for your old mistress.

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Very interesting thoughts fellows, I appreciate it all.

After a talk with my shop.... leaning towards one more local attempt with the Maxwell (vacuum) method. But not committed to that yet.

One unanswered question about a reseal: How do you know the spar/wing internals will not get corroded from stripper going everywhere???

@Bob_Belville As to my 10 years... I've been lucky, all minor stuff, small upgrades, but the plane works for me.. This is for sure the most annoying problem I've dealt with in that the process we used did not work. And quite ironically... I am planning an interior redo very shortly. Fabric is being burn tested now. More impetus to get this damned thing fixed.

Edited by Immelman
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One decade down, another decade to go...

Select permanent solution.  Begin acting on it...

  • Strip and reseal vs. bladders...
  • If reseal, there are at least three or four suppliers with various costs and reputations....
  • If cost is critical, DIY can be successful.  At least two on MS have been documented...
  • Concern for corrosion is always important.  Every tool, material, procedure, has a purpose... and a side effect... always be aware.  Keep both eyes open all the time.

When paying the bill, Keep one eye closed... knowing the pain goes away over time.

Done right, the pain doesn’t return for a couple of decades.  It is really nice not having to continuously think about when the seal is going to let go again.... rain water entering, rust bits forming, fuel exiting, fuel entering the cockpit.... 

A couple of ideas left by My M20C...

Best regards,

-a-

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Very interesting thoughts fellows, I appreciate it all.
After a talk with my shop.... leaning towards one more local attempt with the Maxwell (vacuum) method. But not committed to that yet.
One unanswered question about a reseal: How do you know the spar/wing internals will not get corroded from stripper going everywhere???


I’m no expert but the stripper causing corrosion is not the problem, just like avgas doesn’t cause corrosion. I’ve been told it can damage paint and IIRC someone found corrosion underneath the sealant (apparently water got trapped).
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Water being trapped because of the drain holes plugged can easily cause the corrosion, just as water trapped between a bladder and the spar can cause it. A pro like Paul Beck does not allow the stripper to remain prior to sealing and causing a problem down the road.

Here are a few pics of how it should look.

20180209_102225.jpg

20180209_102229.jpg

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3 hours ago, Immelman said:

One unanswered question about a reseal: How do you know the spar/wing internals will not get corroded from stripper going everywhere???

I think the problem is some older aircraft already have corrosion on the parts that are viewable during the strip process. Some might just cover that up with new sealer but any good shop or IA will want to stop and fix the problem. Sometimes the corrosion is too deep and the spar needs to be replaced which can be costly. 

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On 2/9/2018 at 3:53 PM, mike_elliott said:

want to see sloppy? Here you go... drain holes sealed over, no required topcoat, sealant not on areas it should be, etc.. No wonder this DIY job now requires a pro to fix. Actually I understand it was done by an A&P even. If you dont know why these pics represent a lousy reseal/patch job, you probably shouldn't tackle it yourself. 

Names and N numbers withheld to protect the victim

Left Tank 1.jpg

Right Tank 1.jpg

That job looks lousy, but not because it’s sloppy. It’s lousy because the drain holes were not properly done (as you stated) and there is sealant missing at rivits and fillets. I do not think anyone uses the “cherry juice” top coat any more. 15% more effort would have resulted in a nice tight tank. Truly a shame to go through all that work and half ass the final stretch...

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I am still not understanding (well, yes, I am--FAA, economics, etc.) why there isn't a spray, in a can, that you just reach in there and spray all over the inside of the tank that lasts for say, 5 years. Even if there were two sprays--one to 'prime' the surface over the old sealant and the second to seal the leaks. Jeez lou-eez, just shoot me.

025056031600.jpg

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7 minutes ago, HRM said:

I am still not understanding (well, yes, I am--FAA, economics, etc.) why there isn't a spray, in a can, that you just reach in there and spray all over the inside of the tank that lasts for say, 5 years. Even if there were two sprays--one to 'prime' the surface over the old sealant and the second to seal the leaks. Jeez lou-eez, just shoot me.

Harley, as with all painting and finishing projects, the hard part is preparing the tank surface to accept the new sealant. All of the old sealant must be removed, down to bare metal, then whatever chemicals are used to assist in that must be removed. Much, much preparation, followed by careful aplication with no missed spots and no necesary drain / weep holes covered up. 

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13 hours ago, Shadrach said:

That job looks lousy, but not because it’s sloppy. It’s lousy because the drain holes were not properly done (as you stated) and there is sealant missing at rivits and fillets. I do not think anyone uses the “cherry juice” top coat any more. 15% more effort would have resulted in a nice tight tank. Truly a shame to go through all that work and half ass the final stretch...

The sealant wont adhere to the primer paint anyway. Why would they paint it with primer? A DYI job by an A&P who hasn’t read 65.81 ( requires you to have prior experience for the task; and as one can see, is a good regulation) 

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1 hour ago, HRM said:

I am still not understanding (well, yes, I am--FAA, economics, etc.) why there isn't a spray, in a can, that you just reach in there and spray all over the inside of the tank that lasts for say, 5 years. Even if there were two sprays--one to 'prime' the surface over the old sealant and the second to seal the leaks. Jeez lou-eez, just shoot me.

025056031600.jpg

 . . . and then as it deteriorates clogs your fuel system and causes an off airport landing.

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7 hours ago, mike_elliott said:

The sealant wont adhere to the primer paint anyway. Why would they paint it with primer? A DYI job by an A&P who hasn’t read 61.85 ( requires you to have prior experience for the task; and as one can see, is a good regulation) 

Was the A&P ex-military?  I am pretty sure that I have seen pics of “zinc’d” wet wings in the past, large military AC, not a Mooney. I don’t recall  reading that tank sealant will not adhere to zinc chromate/phosphate primer. Where did you find that information? The sealant used in fuel tanks (CS3204 among others) is also used to seal pressure vessels of pressurized aircraft. I have a hard time believing it won’t adhere to zinc primer. 

Can you link 61.85? I thought all of the mx requirements were outlined  under 43.

 

Edit - The following is stated in the PPG Aerospace TDS for PR1442 Class B

Surface preparation section - Immediately before applying sealant to primed substrates, the surfaces should be cleaned with solvents. Contaminants such as dirt, grease, and/or processing lubricants must be removed prior to sealant application.  

 

Edited by Shadrach
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5 hours ago, Shadrach said:

Was the A&P ex-military?

I Have no idea

 I am pretty sure that I have seen pics of “zinc’d” wet wings in the past, large military AC, not a Mooney. I don’t recall  reading that tank sealant will not adhere to zinc chromate/phosphate primer. Where did you find that information? The sealant used in fuel tanks (CS3204 among others) is also used to seal pressure vessels of pressurized aircraft. I have a hard time believing it won’t adhere to zinc primer. 

My source for this is Paul Beck. If he says it wont, Ill believe him

Can you link 61.85? I thought all of the mx requirements were outlined  under 43.
 

Here ya go MX has to have done it before or be supervised

 

Edit - The following is stated in the PPG Aerospace TDS for PR1442 Class B

Surface preparation section - Immediately before applying sealant to primed substrates, the surfaces should be cleaned with solvents. Contaminants such as dirt, grease, and/or processing lubricants must be removed prior to sealant application.  

Ill ask Paul why he says it wont adhere. He has probably done more tank reseals than anyone. I am sure he has a reason for saying why it will not adhere. It might be like Lyc recommending you run your engine 50ROP :)

 

 

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24 minutes ago, mike_elliott said:

Here ya go MX has to have done it before or be supervised

Thanks Mike, I could not get it to come up on a search of the governments site (it was 4:30AM and I'd yet to be caffeinated, so likely operator error).  I knew there were provisions for actual experience prior to supervising a procedure, but had not reviewed them for a while.  The way I read that, an  A&P that had not applied sealant since A&P school would qualify as long as he had applied sealant while in A&P school.   I think that is fine for a conscientious person who tkes the time to re-familiarize with procedures and materials.   

Paul Beck is indeed an industrial artist. His work commands and is worth a premium.  However, it is possible to get a good tank seal without rising to Paul's aesthetic standard's.   

I look forward to Paul's response re the primer. I'm curious if it's his own tribal knowledge or if there's a manufacturer's recommendation that I've not seen.  It was obviously something the previous A&P thought would improve the quality of the job given that the primer had to be applied after the tank was stripped.   I too think it's odd the tanks are primed (can you imagine trying to use a spray bomb through those access panels?). Has the rest of the wing been primed as well? 

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28 minutes ago, Shadrach said:

Thanks Mike, I could not get it to come up on a search of the governments site (it was 4:30AM and I'd yet to be caffeinated, so likely operator error).  I knew there were provisions for actual experience prior to supervising a procedure, but had not reviewed them for a while.  The way I read that, an  A&P that had not applied sealant since A&P school would qualify as long as he had applied sealant while in A&P school.   I think that is fine for a conscientious person who tkes the time to re-familiarize with procedures and materials.   

Paul Beck is indeed an industrial artist. His work commands and is worth a premium.  However, it is possible to get a good tank seal without rising to Paul's aesthetic standard's.   

I look forward to Paul's response re the primer. I'm curious if it's his own tribal knowledge or if there's a manufacturer's recommendation that I've not seen.  It was obviously something the previous A&P thought would improve the quality of the job given that the primer had to be applied after the tank was stripped.   I too think it's odd the tanks are primed (can you imagine trying to use a spray bomb through those access panels?). Has the rest of the wing been primed as well? 

I dont know Ross, the lousy job pics came from Paul as well as the pretty pics. Weird someone would consider putting zinc primer in the tanks of a Mooney. It looks like Paul still uses the red top coat

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23 minutes ago, mike_elliott said:

I dont know Ross, the lousy job pics came from Paul as well as the pretty pics. Weird someone would consider putting zinc primer in the tanks of a Mooney. It looks like Paul still uses the red top coat

Indeed it does. Goes to show that it depends on who you talk to.  I believe it was Dmax that told me the cherry juice wasn't needed.  I used it anyway, it's the consistency of thin red snot...

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On 2/10/2018 at 9:42 PM, Hank said:

Harley, as with all painting and finishing projects, the hard part is preparing the tank surface to accept the new sealant. All of the old sealant must be removed, down to bare metal, then whatever chemicals are used to assist in that must be removed. Much, much preparation, followed by careful aplication with no missed spots and no necesary drain / weep holes covered up. 

Hank, you missed my point. This mythical spray would seal all the cracks in the existing sealant. If necessary, there would be two parts, one to prime and thus provide a surface for the sealing spray to adhere to.

Jeez, if the current sealant is crumbling or peeling off in sheets, then this obviously would not work.

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On 2/10/2018 at 10:57 PM, LANCECASPER said:

 . . . and then as it deteriorates clogs your fuel system and causes an off airport landing.

No, the mythical spray would not have that property. The 'Leak Stopper' image was just an example of what might be.

Here you go:

Untitled.jpg.7c01c2c49577f584e03755a7bf4d8658.jpg

 

...and now someone is going to ask where to buy the above, just watch.

 

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The Mooney service manual doesn't mention primer and specifically says to clean the surface with MEK immediately before applying the sealant. The MEK would remove any zinc primer I've ever used. There are polysulphide sealants available that contain zinc chromate, but that isn't what is specified. If you were really concerned you could Alodyne the inside of the tanks before applying the sealant.  

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At least based on RV work, tank sealant is applied to bare aluminum that has been roughened and cleaned with solvent.  Intuitively, one can imagine applying it to primer would not have the rough aluminum surface to help with adhesion.  In addition, the adhesion of the sealant would intuitively also be limited to the "sticking power" of the primer.

I'm not sure if this actually results in problems or not, though

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I think primer is the wrong word. I think people meant to say etched. That is how you prep the aluminum surface. 

I could have missed it but I don’t recall seeing anything in the Mooney manual that authorizes priming the tank before sealing  

-Robert

Edited by RobertGary1
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Bladders are permanent. If they leak they can be pulled out the holes they were put in and refurbished in situation for about 1 AMU. Joey Cole told me so himself.

My question to the OP is how long will he keep his airplane. That total reseal won’t impress anyone ten or fifteen years down the road. Like I said, bladders are permanent.

I’ve got 54 gallons in mine, they cost me about 40 lbs, or 6 gallons of avgas, or a suitcase for Mrs. Steingar. I’ve yet to miss the payload.

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