M20k fuel tank reseal

[Invisibleman]

In looking at M20k's for sale, I see quite a few noting fuel tanks resealed.  Is leaking fuel tanks a common issue?  Most say resealed some say bladders installed.  I am wondering what to look for on a used M20k that has not had any reseal.  Who does resealing?  What's involved.  How much does it costs.

thanks

[1980Mooney]

18 minutes ago, Invisibleman said:

In looking at M20k's for sale, I see quite a few noting fuel tanks resealed.  Is leaking fuel tanks a common issue?  Most say resealed some say bladders installed.  I am wondering what to look for on a used M20k that has not had any reseal.  Who does resealing?  What's involved.  How much does it costs.

thanks

Yikes. One of the Achilles heels of a Mooney.  You are going to get a lot of opinions.  The 3 specialty shops in the country charge about $12,000-14,000.  A good seal should last 30 years.  

  

 

[1980Mooney]

Tanks can be patched but few A&P’s have the skill (or patience)  to do it right.  Old leaking seal has to be removed in preparation. Done wrong, the mechanic will disturb (lift) good seal and worsen the problem.

The actual source of leak is usually hard to find since it may run along the inside of the wing before you notice it. You have to fill the tank with soapy water and either blow air on the outside of the wing or pull a vacuum to observe and pinpoint  the source of the leak  

Fortunately I have a mechanic who knows how to do it right.

 

[dzeleski]

43 minutes ago, Invisibleman said:

In looking at M20k's for sale, I see quite a few noting fuel tanks resealed.  Is leaking fuel tanks a common issue?  Most say resealed some say bladders installed.  I am wondering what to look for on a used M20k that has not had any reseal.  Who does resealing?  What's involved.  How much does it costs.

thanks

At this point nearly every Mooney produced has had either bladders installed or a reseal. You do not want to search for M20Ks that have never been resealed as thats not actually a good thing. I believe the last K was made in 1998, even that sealant is +20 years old at this point.

Mooneys leaking is considered a part of ownership the service manual spells out to what degree its ok or not. Patches are common as well.

https://www.weepnomorellc.com/faq.html

Edited December 20, 2024 by dzeleski

[1980Mooney]

 

[1980Mooney]

Not everyone is happy with the 3 specialty shops located in Florida, Minnesota and outside Houston. Sometimes owners fly halfway across the country, wait months, get it back and it leaks.  Read the pireps  

 

[1980Mooney]

 

[Marc_B]

Wet wings are an accepted and widely used practice of using the inside of the wing structure as a fuel cell.  The issue is that the sealant has a life span that can last up to 30-40+ years if hangared and kept wet with fuel.  Over time the sealant contracts and becomes brittle and eventually begins to pull away or break down allowing leaks.  Often these leaks may track along ribs and exit the wing at a location distant from the source of the leak.  Some leaks can be uncovered and "patched" but often the material applied for the patch (especially if just applied over old sealant) will also contract on curing and just put more tension on the old sealant.  So depending on the overall age and condition of your sealant, sometimes it just makes more sense to have the entire wing resealed.

I've used WeepNoMore, and Paul Beck is one of the well known tank resealers that has developed his techniques for removing and resealing to an art and stands behind his work.  You'll also find good reviews from others about Wet Wingologists.  There are a few shops (i.e. Don Maxwell) who have had good experience with patching, but sometimes this is ultimately just kicking the can down the road a bit; but that also depends on the overall condition of your sealant in general.

For cost comparison, having two tanks resealed in 2022 cost just under 9k and was billed at about 100 hrs (aka it's a handful of chemicals and a crap ton of work!).  I could have waited longer for reseal but I wanted to get this done before repaint.

[LANCECASPER]

1 hour ago, Invisibleman said:

In looking at M20k's for sale, I see quite a few noting fuel tanks resealed.  Is leaking fuel tanks a common issue?  Most say resealed some say bladders installed.  I am wondering what to look for on a used M20k that has not had any reseal.  Who does resealing?  What's involved.  How much does it costs.

thanks

You won’t find any M20Ks with bladders. The STC on bladders does not cover anything newer than a J model.

Going forward, after a reseal in Minnesota or Florida, a lot has to do with how the Mooney is maintained. If the tanks are kept low on fuel the sealant will dry out faster. If the airplane is kept outside in extreme temperatures the sealant will not last as long. If it is kept low on fuel and outside, that’s even worse. If the shock discs, the only shock absorption on a Mooney, aren’t changed when they should be they become hard and don’t absorb any shock, which is tough on aging sealant in the seams. 

[Marc_B]

And just to be clear, not all seeps and leaks are an airworthiness issue or flight hazard.  Some are very slight and not an issues other than leaving a blue "fingerprint" when it dries.

[NickG]

7 minutes ago, Marc_B said:

Wet wings are an accepted and widely used practice of using the inside of the wing structure as a fuel cell.  The issue is that the sealant has a life span that can last up to 30-40+ years if hangared and kept wet with fuel.  Over time the sealant contracts and becomes brittle and eventually begins to pull away or break down allowing leaks.  Often these leaks may track along ribs and exit the wing at a location distant from the source of the leak.  Some leaks can be uncovered and "patched" but often the material applied for the patch (especially if just applied over old sealant) will also contract on curing and just put more tension on the old sealant.  So depending on the overall age and condition of your sealant, sometimes it just makes more sense to have the entire wing resealed.

I've used WeepNoMore, and Paul Beck is one of the well known tank resealers that has developed his techniques for removing and resealing to an art and stands behind his work.  You'll also find good reviews from others about Wet Wingologists.  There are a few shops (i.e. Don Maxwell) who have had good experience with patching, but sometimes this is ultimately just kicking the can down the road a bit; but that also depends on the overall condition of your sealant in general.

For cost comparison, having two tanks resealed in 2022 cost just under 9k and was billed at about 100 hrs (aka it's a handful of chemicals and a crap ton of work!).  I could have waited longer for reseal but I wanted to get this done before repaint.

My understanding is that Don Maxwell is doing complete tank reseals and providing a 7-year warranty. They now own the Monroy LRT STC so they are doing a fair amount of tank work. Price around the same as the other shops. I spoke with them a couple of months ago.

[1980Mooney]

12 minutes ago, NickG said:

My understanding is that Don Maxwell is doing complete tank reseals and providing a 7-year warranty. They now own the Monroy LRT STC so they are doing a fair amount of tank work. Price around the same as the other shops. I spoke with them a couple of months ago.

And what is the current “price range” that is just “about the same” amongst all the shops?

[NickG]

13 minutes ago, 1980Mooney said:

And what is the current “price range” that is just “about the same” amongst all the shops?

If I remember correctly, it was around 6-7k per tank for my Ovation but obviously give them a call to quote the aircraft you have.

[DonMuncy]

My K model is from 1982 and it has never had a reseal. I had one small spot on the top (in the wing walk; very easily repaired), but no leaks otherwise. Mine may start leaking tomorrow, but sometimes they last a LONG time. 

If I was buying a K model that was not still under warranty from a reseal, I would probably figure in about 1/2 the price of a reseal discount, on the assumption that it is about 50% likely to need one sometime soon. Probably most sellers have theirs priced on this basis already.

[Fly Boomer]

2 hours ago, NickG said:

My understanding is that Don Maxwell is doing complete tank reseals and providing a 7-year warranty. They now own the Monroy LRT STC so they are doing a fair amount of tank work. Price around the same as the other shops. I spoke with them a couple of months ago.

I assumed Maxwell was using the guy in Houston for complete re-seal jobs, but I forgot about the Monroy deal.  He probably has a guy on staff now.

[Z W]

I've had leaks patched by small local shops a few times, at a cost of a few hundred dollars here and there. My tanks have not been fully resealed since 1982, as far as I can tell from the logs.

It's a maintenance item, but nothing to be too concerned about. Every model of plane has its maintenance issues. Cheaper than a parachute repack.

You could also buy a plane that was resealed 5 years ago and have it start leaking after your first bounced landing, so just be prepared. Many (most?) leaks can be left alone until the next annual or the next time it's in the shop. They result in stains on the wings but often the fuel evaporates before it even drips on the ground. I've never had one that was a flight safety issue or would ground the plane.

[M20F]

Two key things. 
 
1.). As others point out first step is determining if it is a leak that needs to be addressed.  
2.)  Determine if it can be patched.  A link on Maxwell doing it is provided.  He patched my left tank for I want to say $800 two years ago.  I will echo you need to find somebody who knows how to do it.  It is an art not a science.  
 
For whatever reason tanks are like engines (one cylinder has compression of 68 should I top or overhaul), everyone wants to go the whole distance without even trying the smaller things.  

[Red Leader]

Take it to someplace reputable. Pay the extra because the alternative is even more expensive. A couple of years ago, one of my tanks suddenly developed a leak that was fairly severe. I had it fixed at a shop on my home field at a price exceeding 2k. My first fill of the tank (a couple of weeks later to ensure a good cure) and it leaked. To me. that the leak was coming from the same location, at the same rate and stopped at the same level. The same shop fixed the leak again and charged me another 2k, claiming it was a different leak. That totally pissed me off as it was OBVIOUSLY the same leak that was improperly repaired the first time. Lesson learned - take it to someplace reputable. 

[Invisibleman]

All great responses to my inquiry.  Very helpful.  Lots of great information.  Thanks so much.