DIY Cleaning the fuel tanks for a reseal - what to strip the old sealant with

[bcg]

We patched a small leak in one of my tanks at annual last week and when we were in there, it became pretty apparent that a reseal was on order.  The sealant is starting to bubble up and will be pulling away before much longer, it looked bad.

 

Since I'm flying a C with the small tanks, I thought I'd attempt this myself on one side instead of taking it somewhere.  I've read mixed reviews on that idea, some people said they wish they'd never started it and others said it wasn't all that bad.  For those of you that have done this and didn't think it was all that bad, what process or chemical did you use to strip the old sealant off?  Did you just scrape it off manually or is there something I can put on it to soften it up first?  Any tips are appreciated.

[KSMooniac]

Polygone is the product you're looking for.  There is a liquid and gel version, and both are helpful from what I read many years ago when I contemplated doing this myself.  I took it to Weep-no-more instead and wrote a big check, and don't regret that choice at all.  Paul at W-n-M pretty much invented a process using those products along with a recirculating pump and filter system to get most of the sealant out, which minimizes the hand work inside the tank.  I figured I might be able to get all of the old stuff out, but I would not know all of the tricks of the trade for putting new sealant down, and that was worth paying the pro to be done with it, versus chasing leaks forever if I missed some little nook or cranny.  YMMV, of course!

[bcg]

3 minutes ago, KSMooniac said:

Polygone is the product you're looking for.  There is a liquid and gel version, and both are helpful from what I read many years ago when I contemplated doing this myself.  I took it to Weep-no-more instead and wrote a big check, and don't regret that choice at all.  Paul at W-n-M pretty much invented a process using those products along with a recirculating pump and filter system to get most of the sealant out, which minimizes the hand work inside the tank.  I figured I might be able to get all of the old stuff out, but I would not know all of the tricks of the trade for putting new sealant down, and that was worth paying the pro to be done with it, versus chasing leaks forever if I missed some little nook or cranny.  YMMV, of course!

Thanks, I've got good, very experienced support for putting the new sealant on if I can get it off.  He uses MEK to take it off for patches, I just wasn't sure if there might be a better option.  I've been told that the method of pumping through the tank will result in some paint removal as the sealant goes away and it starts to leak out, did you experience much of that?  I could easily build a recirculating system with a pump and some spray nozzles but, I don't want to damage the paint since it's in pretty good shape.

[KSMooniac]

There wasn't much or any paint loss that i noticed except immediately at the edges of access panels and screw holes... Hard to avoid it. But no areas of gross acreage loss. I don't think the polygon removes paint.

My original paint was 31 years old at the time, and I re-painted about 18 months later so it wasn't a big concern for me at the time.

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[bcg]

There wasn't much or any paint loss that i noticed except immediately at the edges of access panels and screw holes... Hard to avoid it. But no areas of gross acreage loss. I don't think the polygon removes paint.

My original paint was 31 years old at the time, and I re-painted about 18 months later so it wasn't a big concern for me at the time.

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Thank you. I won't do anything before April or May at the earliest. I may buy some Polygone and test it on some painted airplane parts to see how it reacts. I can deal with a little around the panels, I just don't want to have to repaint the bottom of my wings or my mains after stripping the sealant.

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[Mark89114]

There is a well written thread on here somewhere where poster does it himself.  He built a spray rig, etc.  

My mechanic says if you want to hate your airplane do this yourself.  

I am going to say something stupid and based on what I have read on the internet and seen in my own tank.  The application doesn't look hard, as sloppy as my factory stuff it must not be mission critical.   YMMV

[christaylor302]

I’m just finishing a complete strip and reseal of both tanks on a M20C. It’s definitely a labor of love. Polygone Gel and plastic scrapers worked best for me. Also some tile grout brushes work well, plastic bristle type. It will eat the paint if you let it sit on it. If you get some on the paint a quick rinse with a spray bottle of water and paper towels to wipe it up will save it. You need to mix up the bucket of Polygone Gel and keep it covered for best results. I used 3 5lbs buckets total. I also used a gallon of Klein Strip paint thinner (California version) that was labeled a MEK alternative.


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[bcg]

4 hours ago, christaylor302 said:

I’m just finishing a complete strip and reseal of both tanks on a M20C. It’s definitely a labor of love. Polygone Gel and plastic scrapers worked best for me. Also some tile grout brushes work well, plastic bristle type. It will eat the paint if you let it sit on it. If you get some on the paint a quick rinse with a spray bottle of water and paper towels to wipe it up will save it. You need to mix up the bucket of Polygone Gel and keep it covered for best results. I used 3 5lbs buckets total. I also used a gallon of Klein Strip paint thinner (California version) that was labeled a MEK alternative.


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Thanks, that's really helpful.  Knowing what you know now, would you do it again?

[bcg]

13 hours ago, Mark89114 said:

There is a well written thread on here somewhere where poster does it himself.  He built a spray rig, etc.  

My mechanic says if you want to hate your airplane do this yourself.  

I am going to say something stupid and based on what I have read on the internet and seen in my own tank.  The application doesn't look hard, as sloppy as my factory stuff it must not be mission critical.   YMMV

I've read several threads on here about this task including one from around 2020 where someone was building a recirculating system.  I think building something to recirculate the solvent would be easy enough, I probably have everything I'd need to do it in the shop already. 

 

The consensus seems to be not to do this yourself but, I'm hard headed and have to experience things for myself.  I'm sure it's time consuming and tedious but, it isn't really difficult.  I'm pretty good and zoning out and working on mind numbing tasks, like standing at a blast cabinet for 2 - 3 hours.  Sometimes it's actually nice.  I'm also not a big guy at 5' 6" and 130 pounds so, it should be a little more comfortable for me than it would be for a bigger guy.

[christaylor302]

Thanks, that's really helpful.  Knowing what you know now, would you do it again?

I’m working on a restoration project so flying it somewhere to be done was not an option. There is also some pride in knowing I did it.

But, if you fly regularly and the money is not going to bankrupt you, you might be better off having someone else do it. I suspect they’ll only have the plane for a week or so versus the months it took me working nights and weekends. I spent about $3,000 between the chemicals, tools and all the sealant. I followed the Mooney service manual for resealing.

So far this is the hardest part of the restoration project.


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[KSMooniac]

I think the typical flow time is on the order of 3 weeks or more for a pro shop to do it.  That was my experience in 2008.  Several days of poygone circulation, some days for manual cleaning and prep, and some days for application of new sealant.  Then it needs to sit for a period of time to fully cure, and then fill the tanks and let it sit for several days to check for leaks.  It adds up.

[bcg]

I think the typical flow time is on the order of 3 weeks or more for a pro shop to do it.  That was my experience in 2008.  Several days of poygone circulation, some days for manual cleaning and prep, and some days for application of new sealant.  Then it needs to sit for a period of time to fully cure, and then fill the tanks and let it sit for several days to check for leaks.  It adds up.

I think I could probably get it done on my own in the same timeframe. 2 weeks to strip, a week to seal and test the tanks. I like doing stuff myself and I have the time, it'll be more convenient than taking somewhere if it doesn't turn into an absolute s-show. I'm expecting tedious, time consuming work to strip it.

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[christaylor302]

I think I could probably get it done on my own in the same timeframe. 2 weeks to strip, a week to seal and test the tanks. I like doing stuff myself and I have the time, it'll be more convenient than taking somewhere if it doesn't turn into an absolute s-show. I'm expecting tedious, time consuming work to strip it.

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You might want to do one tank at a time. That way if it does turn into a s-show, you can fly it somewhere on the second tank.

[Fritz1]

Tough call, there are about 3 shops in the US that do this well, they are typically booked 9-12 months out and do a good job, airplane sits in the shop 2-3 weeks and you have to get it there, sooo, how many hours is the do it yourself job going to take, what are these hours going to cost you versus paying somebody that does 50 airplanes per year. Every job has a learning curve. My tanks were done by Weep no more 5 years ago and they don't leak. Flew the bird to Wilmar, picked it up about 2 weeks later. Oasis is an excellent Mooney shop, they can fix other stuff while the bird sits there. No regrets. 

[bcg]

You might want to do one tank at a time. That way if it does turn into a s-show, you can fly it somewhere on the second tank.

That was my plan. Left tank isn't leaking at all so I'm not messing with it. Right tank has a slow seep that needs to be addressed but, it's only like 1/2 gallon overnight on a full tank and then it stops so it's up high and isn't critical. I just don't fill it until right before departure and fly off the right tank first right now.

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[LANCECASPER]

Or . . . drop it off with Edison at Wet-Wingologists at KFXE while you're in S. Florida and have him do it since it's already there. He can usually work people in to his schedule.

[bcg]

Or . . . drop it off with Edison at Wet-Wingologists at KFXE while you're in S. Florida and have him do it since it's already there. He can usually work people in to his schedule.

Where's the fun in that?

I actually want to try this myself. I realize I may very well regret it but, I like to see if I think things are really as bad as people say they are. Sometimes, it turns out that everyone was 100% correct and I make a mistake. At least I learn something in the process.

Everyone of us in this group disregard "common knowledge" to some extent or we wouldn't be flying cramped, difficult to land airplanes that will instantly go into an unrecoverable spin if stalled and mechanics hate to work on...

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[LANCECASPER]

22 minutes ago, bcg said:

Where's the fun in that?

I actually want to try this myself. I realize I may very well regret it but, I like to see if I think things are really as bad as people say they are. Sometimes, it turns out that everyone was 100% correct and I make a mistake. At least I learn something in the process.

Everyone of us in this group disregard "common knowledge" to some extent or we wouldn't be flying cramped, difficult to land airplanes that will instantly go into an unrecoverable spin if stalled and mechanics hate to work on...

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Hey I get it - some of us just have to make sure for ourselves that the burner is hot. . .lol




It wouldn't hurt to stop by his shop and get a quote and pick up a little intel on how he does it.

[M20F-1968]

I can give you some of my personal experiences.  I have an extensively rebuilt and highly modified F that is more than a Factory J would be.  

I stripped the early into the project, with an A&P's helper and then myself doing the work.  Years later I had two guys from Gulfstream doing mostly sheet metal work on the plane.  The sheet metal work of the primary guy was first-rate, to the level that it was better than factory work, and as good as Beegle's in Colorado, which is saying a lot.

Both had some experience sealing tanks and to fly the plane I needed tanks sealed.  There were leaks after they finished which they tried to seal.  It was good enough to fly to plane from point A to point B, but was not good enough to be the finished product.  

I took the plane to Paul Beck who completely stripped and resealed the tanks.  If the two Gulfstrean guys could not do it, an owner who has never done tank work before will have leaks.  Stripping both tanks will make the plane unairworthy.  Stripping one tank will still allow you to fly it, but the shop you take it to will need to strip and reseal the other tank as well.  You are not be gaining much, if anything at all.  It is terrible, messy grunt work.  There is really nothing to gain except maybe making a recycling device, testing your knowledge of fluid dynamics, for a device you will likely use once, maybe twice depending on how old you are.  

Give Paul Beck, Weep no More a call.  He will advise you well.

John Breda

[MikeOH]

@bcg

Sounds like you're a DIY guy like myself.  Don't let all these naysayers talk you out of some honest HARD work.  Frankly, I've considered doing the same when my tanks get bad.  I fully realize it's going to be an arduous job but honestly doubt it's going to take more than a few solid 8 hour days to strip a tank (20-30 hours); I'll be most interested in your feedback should you accept the mission!  Use the proper sealants and carefully apply and I don't think the 'skill' level is some 'off the charts' expertise that some here would have you believe.  A top heart surgeon is probably not the guy to do a good job cleaning your pool, for example

What are the materials going to run, 1 AMU?  And, what's a tank reseal these days $8,000?  I'll work pretty hard to save $7,000...the old 'what's your time worth' always falls on deaf ears to me...it's not like I'm getting paid when I'm sitting on the couch.  Even more so now that I'm retired!

Good luck!  I'm rooting for you, anyway

[bcg]

[mention=50484]bcg[/mention]
Sounds like you're a DIY guy like myself.  Don't let all these naysayers talk you out of some honest HARD work.  Frankly, I've considered doing the same when my tanks get bad.  I fully realize it's going to be an arduous job but honestly doubt it's going to take more than a few solid 8 hour days to strip a tank (20-30 hours); I'll be most interested in your feedback should you accept the mission!  Use the proper sealants and carefully apply and I don't think the 'skill' level is some 'off the charts' expertise that some here would have you believe.  A top heart surgeon is probably not the guy to do a good job cleaning your pool, for example
What are the materials going to run, 1 AMU?  And, what's a tank reseal these days $8,000?  I'll work pretty hard to save $7,000...the old 'what's your time worth' always falls on deaf ears to me...it's not like I'm getting paid when I'm sitting on the couch.  Even more so now that I'm retired!
Good luck!  I'm rooting for you, anyway

That's a big part of it, I'm basically retired myself so I've got the time, I'd rather be doing something than nothing.

I'm going to have Dugosh do the sealing part, David and I have already talked about it. I know he'll do a good job and I won't have any leaks when he's done so I'm not really worried about that part. I just need to do the mindless grunt work and there's something cathartic about just zoning out and doing manual labor for me.

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[christaylor302]

Yes, it’s not skilled work. Just messy, tedious around the rivets, a LOT of time, and resealing is also messy.

[N201MKTurbo]

Stripping the tank is doable. It just takes a lot of work. 
 

Applying the sealant should be done exactly as the maintenance manual says. Don’t use any “better” methods or material.

[Bartman]

I took mine to Edison in Jan 2008.  Had one leak 14 years later from a screw under the wing walk which I fixed with a SMALL amount of Permatex #3. 

17 years later I remain very happy. 

[turbofan]

I emailed Paul a few months ago regarding my 69 F and he's booked out to 2026, probably farther now. My left tank needs it, right is fine. When I bought the plane a few months ago there was old evidence of leaking but nothing active. Now I'm flying off a short grass strip (1500 ft) with some bumps and it's leaking quite a bit now. I did an RV4 set of tanks a few years ago, messy, horrible, toxic, aggravating........but doable.