Time for tanks to be resealed?

[RobertE]

I've got an M20J. There are four flush rivets at the bottom and toward the rear of the right tank that show blue staining. These are the rivets just in front of the wheel wheel and are in the area in which it appears there is a double row of rivets.

Is this an early sign of a needed resealing? And does anyone know why these four would show evidence of fuel seepage while those a quarter of an inch in front of them do not?

Thanks.

[rbridges]

99% sure that you have a slow leak starting. Fuel leaks can start, roll and exit in different places. You can live with a slow leak for a while, but you will eventually need to address it.

If you want to open a can of worms, start a thread asking if you should reseal or get bladders.

[Hank]

You may, sadly, have a fuel leak. My advice is to monitor the situation. Clean it up and see how quickly it reappears. If you are in a hangar, a leak during cold weather will eventually leave blue spots on the floor because it will evaporate more slowly, giving it time to run and drip. Leaks often "appear" during a cold snap, and "cure" when it heats back up, simply due to contraction/expansion of the sealant due to temperature, and the faster evaporation rate during warm weather.

Prepare yourself either way. Downtime, labor and round-trip travel somewhere--all of my good options were 700 nm or more, in three different directions. Once properly done [i.e., not a quick patch job somewhere; I did that, and in two years the leak was much worse than before and off I went to reseal], you should have many trouble-free years.

[Marauder]

I've got an M20J. There are four flush rivets at the bottom and toward the rear of the right tank that show blue staining. These are the rivets just in front of the wheel wheel and are in the area in which it appears there is a double row of rivets.

Is this an early sign of a needed resealing? And does anyone know why these four would show evidence of fuel seepage while those a quarter of an inch in front of them do not?

Thanks.

The first sign of my tanks failing were the bluish stain around the rivet heads on top of the wing. Later I developed an active leak in the wheel well area on one side. I also started noticing a fuel odor inside of the cockpit as well. Hopefully this is not the start of leaks for you...

[Lood]

Just fill your tank and let it stand over night. Dip it the next morning and see how much fuel is gone. Then do the maths and decide how much you're going to loose in anyway.

My managed and lived with my seeping left tank for almost 5 years, but now, depending on its level, it's leaking at a rate of about 5 gals every 3 - 4 days, so it's time to bite the bullet. I had the right tank resealed earlier this year and it gives me immense pleasure to always find its fuel level where I left it - even after weeks.

[gregwatts]

I just went thru a similar episode. My right tank was showing the same fuel stains in the same location as what you describe. I let it go for about 10 months but started noticing that the tank was taking in a lot of water whenever it rained. Water gets in wherever fuel gets out!!!!

I just had to bite the bullet and take it to Wetwingologists in FXE.

[Steve65E-NC]

Like many other posters here, you want help but do not give us sufficient information to help you. Where are you located? Don Maxwell has great technique in solving this type "early leak" problem. If you are anywhere near Texas, give him a call and take the airplane there. Otherwise, print off his article on the subject and discuss it with your local A&P.

[rbridges]

The first sign of my tanks failing were the bluish stain around the rivet heads on top of the wing. Later I developed an active leak in the wheel well area on one side. I also started noticing a fuel odor inside of the cockpit as well. Hopefully this is not the start of leaks for you...

that's right. I forgot about the fuel smell in the cockpit. I always had to open the doors and let it air out during my preflight. Glad that's gone.

[Piloto]

Winter is the leak season. You may have not seen this leak during the summer due to quicker fuel evaporation due to higher temperatures. Fuel tank leaks are more of an esthetics issue than a flight hazard, unless you have a drip. On an old DC-10 you may need an umbrella when walking underneath the wing to board the plane. Keep an eye on the leak and have it reseal when the looks bothers you.

José

[John Pleisse]

My theory? Patch first, up to $3k, then toss in th towel for a reseal or bladders. Have Mooney people do it (patch work), not amatuers. You'll save time and aggravation. There are multiple schools of thought on why tanks leak. I am a firm beleiver that hard landings, cross load landings and high speed taxi turns are often the culprit. Old seal? Sure, but something has to precipitate a leak, weep or seep. I say patch and go easy on your ground ops.

Also, which wheel well, R or L? Anything starboard wheel well or inward is a deal breaker and must be addressed asap. Too close to muffler exhahust and exhaust stream.

[Alan Fox]

How old are your gear donuts , This is the main reason these things leak.....You may slow down the inevitable by replacing them if they are more than 15 to 20 years old...

[bnicolette]

Hey guys speaking of gear donuts I was reading in the service manual recently and it says to spray graphite powder on these every 50 hours. Is this something that you guys have been doing? I haven't been I suppose I should be. Any products you guys recommend for this?

Don't mean to rob this thread.

[Piloto]

Hard landings or worn out donuts have no impact on the sealant. Think about it for a moment. If you can shake the wing rivets to the point of breaking the sealant you would have a loose structure when you add all the rivets in a line doing this. Sealant can stretch 0.020" without breaking. If you take a line of 50 rivets wobbling 0.02" you would have a 1 inch structural deflection at one end. Like in any rubber material what causes sealant failure is heat, age and application. Keep your tanks at least half full if tied down outside. This will keep temps lower. When applying new sealant make sure you have clean bare metal. Let it cure for at least two days at 70F or higher. Remember is not a genuine Mooney unless it has some minor stains.

José

[fantom]

New donuts also give a firmer taxi ride than old ones, in my experience, so I don't believe old ones cause leaks.

[John Pleisse]

I have 33 year old sealant in my J model. Patch work has been proportional to rough landings/ground ops. I land softly and taxi slow, I don't get leaks. This theory is further bolstered by reseal jobs not holding up (not all work or sealant is bad) and the fact that many new Ovations and Acclaims often have tank leaks, regardless of the sealant used (and they have had pronblems with more than one). i would also add, I have had two 30 year MSC IA's proporting this notion as well.

[DonMuncy]

I have had my 231 for 12 years with no fuel tank leaks. I have probably had more hard landings than average. Naturally this doesn't prove anything, but might lead one to think that hard landings are a significant cause of leaks.

[Hector]

I land softly and taxi slow, I don't get leaks. This theory is further bolstered by reseal jobs not holding up .

There is truth to both arguments. Polysulfide sealants will embrittle with age, heat, and other factors. At some point, regardless of how smooth your landings are, you will develop leaks. That being said, take old embrittled sealant and subject it to high strains from harsh landings, high G maneuvers, etc and you compound the problem. Without question, however, age is the biggest factor unless you had a crappy sealant application to begin with.

Sent from my iPad using Tapatalk HD

[DaV8or]

I have developed my first leak as well. It's coming out of one of the lower tank access panels. I'm living with it for now. At some point I'll call around about a patch job. No way I'm going for a strip and reseal, or bladders right now.

[ChristianGodin]

I leave in Montreal, Canada. my J is allways in a heated hangar. I have the same problem. Stain on the passenger side and smell in the cockpit. My APP tells me I don't have to do anything before it leak.

For those that when through, is it better reseal or bladder? And what is the average cost?

[Alan Fox]

New donuts also give a firmer taxi ride than old ones, in my experience, so I don't believe old ones cause leaks.

New Donuts are way bouncier than old ones...Old sealant cracks....I have resealed tanks , and can see that the cracks are almost always at the spars and the inspection panels.....Hard landings cause carcks in the sealant......

[DaV8or]

Hi Christian,

I have not gone through it, but I have watched the debates on here and elsewhere for a while now. I'll try to summarize.

The cost difference seems to be about $8,000 for strip and reseal vs. about $10,000 for bladders in US dollars. In the past, the bladders were the clear choice, but a new process has made the strip and reseal a lot cheaper and of a higher quality, so the debate continues. It really comes down to the individual.

Hope this helps.

[N201MKTurbo]

My reseal cost almost $9000.00 not including the transportation, and they did a lousy job. It was done at Wilmar...

[aviatoreb]

My reseal cost almost $9000.00 not including the transportation, and they did a lousy job. It was done at Wilmar...

What was lousy about it? Is it not holding? I am sorry to hear - That's a lot to pay for a lousy job.

[N201MKTurbo]

I have wrote about it before.

They didn't have it finished when promissed, after I bought tickets to pick it up and took time off work.

They ruined the paint on the landing gear, wheel wells and portions of the wing and fuselage. It took me about 30 hours of work to fix it.

It started leaking within two weeks, I'm sure they would have fixed it, but the logistics and cost of taking it back were prohibitive.

I have done two repairs to the right tank, each one took about 12 hours of my time.

The right tank is now leaking.

When I was fixing the tank I noticed that there was no bead of sealant applied, only a brush coat. The Mooney service manual is very specific about this.

The only place there was the red liquid butal rubber applied was in the cells that you can see through gas caps, I can only assume they were trying to cut corners and decive me.

[N201MKTurbo]

I ment the left tank is now leaking. I havn't opened it up yet, so I don't know how it was done.