how common are persistent fuel tank leaks?

[philip_g]

maybe a stupid question, but I'm looking at the logs on a completed and flying 10 that is for sale, and it seems like every year or two since new, the builder has had to chase fuel leaks in both wing tanks. coming from mooneys, that's usually a sign that the tank seals are failing and need to be redone to the tune of about 15k. on the mooney, once they're redone they're good for a couple decades and don't leak usually unless something like a gasket at the base of the tank where the fuel senders sit fails. most puzzling is pretty recently an a&p went in and patched some for them in the left tank this year, the left seems the most troublesome for them.

I guess I'm asking if the tanks just weren't sealed well during construction, or if it's just something that happens periodically and that is just a minor annoyance to be dealt with. and if it is abnormal, is it a major hassle or even possible to at some point just remove the tanks and completely reseal them or is it something that you have to take the plane to someone like weep no more in MN like you would a mooney that has the tools to get in there and seal them in place?

[rleffler]

Originally Posted by philip_g

maybe a stupid question, but I'm looking at the logs on a completed and flying 10 that is for sale, and it seems like every year or two since new, the builder has had to chase fuel leaks in both wing tanks. coming from mooneys, that's usually a sign that the tank seals are failing and need to be redone to the tune of about 15k. on the mooney, once they're redone they're good for a couple decades and don't leak usually unless something like a gasket at the base of the tank where the fuel senders sit fails. most puzzling is pretty recently an a&p went in and patched some for them in the left tank this year, the left seems the most troublesome for them.

I guess I'm asking if the tanks just weren't sealed well during construction, or if it's just something that happens periodically and that is just a minor annoyance to be dealt with. and if it is abnormal, is it a major hassle or even possible to at some point just remove the tanks and completely reseal them or is it something that you have to take the plane to someone like weep no more in MN like you would a mooney that has the tools to get in there and seal them in place?

I suspect your assumption about the tank build quality is accurate. No it isn?t normal.

1. If the tanks has defects, are there other issues with the build you havent found yet? I would do an extremely detailed pre-buy by somebody very familiar will the typical issues.

2. The tanks can be fixed. Cutting a hole in the back baffle so that you can re-applying proseal correctly. You then will have to seal your new access panel. You can also see the weeping rivets with a little green loctite and a small vacuum, but that will trash your paint job.


It?s doable, is the rest of the aircraft in a quality state that you want to go through the expense and effort with the tanks?

[9GT]

If its a quick build wing from Vans, those are prone to leaks. You can see and read what I found when I opened up the factory quick build tanks on my -9A here: http://www.vansairforce.com/communit...d.php?t=158234

[N941WR]

If slow build tanks, it depends on how they were built.

There is a lot of bad advice on this forum about easier ways to build the tanks. If the builder disregarded the bad advice and followed the instructions, they probably won't leak.

The problem is that the tanks will hold pressure and paint blisters won't show up for a a few years later.

[philip_g]

Thanks for the insight Bob, I guess you kind of read into my thoughts and concerns without me having to say them.

I haven't seen the plane yet, I have to fly down to see it about 3 hours each way, so I'm just reviewing the logs. The builder appears to have kept and flown the airplane 1k hours in 10 years and kept pretty detailed logs so that's a good sign. But my concerns are the same as yours I think.

It's priced I believe fairly low.


It's listed by a broker, while still registered to the builder. I'm not sure if maybe the builder passed away or something along those lines but that's odd to me. Builder repairs the entire life of the airframe and recent a&p repairs could indicate that's the case, unfortunately. Also the plane is adsb out and hasn't flown in 6 months according to flight aware.


Doesn't appear to be a vaf member, not a deal breaker but a real bummer.


I have a good Mooney and Cirrus shop I've worked with for years but I haven't begun the process of trying to decide how to get a pre-purchase inspection done on an e-ab airplane. I'd want a good borescope done, the history indicates low compression on one jug and a suspected sticky valve some time ago and now magically at the last condition inspection probably done at the request of the broker the compression looks really good across the board. Builder ran a quart of MMO in the sump at every change. Not sure how I feel about that.

[philip_g]

Originally Posted by N941WR

If slow build tanks, it depends on how they were built.

There is a lot of bad advice on this forum about easier ways to build the tanks. If the builder disregarded the bad advice and followed the instructions, they probably won't leak.

The problem is that the tanks will hold pressure and paint blisters won't show up for a a few years later.

Can't tell if it was a QB or a sb from the logs. Wonder if vans would be able to tell me from the serial number.
If memory serves the plane first flew in 09 so they've had lots of time to show up.

Guess I'm a bit twitchy about leaky tanks from owning mooneys where it's kind of a big deal to have them stripped and resealed, I mean, it's not really a tank it's the wing on the Mooney so kind of a different beast as near as I can tell.

[Plummit]

Originally Posted by rleffler

I suspect your assumption about the tank build quality is accurate. No it isn’t normal.

When I thought that Van's might repair my Quick build tanks that have leaked incessantly due to poor quality work-manship, Sterling Langrell wrote this in an email to me:

"I did receive the pictures and have been looking over them and discussed this with my boss. The location of the leaking rivets is a place we have seen from time to time as it is a location that can potentially get some foot traffic being right next to the wing walk area, sitting or walking on sealed rivets can cause the seal to fail. Given that this is a second hand kit paired with the age of it I am not able to offer a "warrantee" repair on this tank.

We have had similar leaks on our factory 10 caused by people stepping and sitting on this area. We have had luck with sanding the paint away and applying a thin dime size dollop of tank sealant on the exterior. There will be a small amount of buildup on the outside but the tank sealant can be painted and is not very noticeable in the end"

So fuel tanks leaks on the top rivets should be expected. You be the judge if you want to repair rivet leaks with a "dollop" of tank sealant. BTW, the original builder of my plane told me that the QB tanks leaked "like a sieve" from the very beginning. I have no reason to dis-believe him after the stories I've read from other QB builders.

-Marc

[Mark33]

I did a preemptive strike on my quick-build -7 tanks and sent them off to Paul at Weep No More. He opened up the rear baffles, completely stripped out all of the pro-seal, and re-sealed everything with his special sealant. I?m still in the building process so I haven?t tested the tanks out yet, but I have full confidence that my tanks will be leak free for the life of the airplane. It?s a little bit pricey to have this done, but I guess peace of mind has a certain value.

[N941WR]

Originally Posted by philip_g

...
Guess I'm a bit twitchy about leaky tanks from owning mooneys where it's kind of a big deal to have them stripped and resealed, I mean, it's not really a tank it's the wing on the Mooney so kind of a different beast as near as I can tell.

The good thing about an RV is the tanks are just bolted and screwed in, similar to a Cherokee. However, there is a good chance the paint will get messed up.

One solution is to turn off the fuel, drain the tank, put a vacuum on the tank via the vent line, and put some green wicking loctite on it. That may seal leaking rivets.

Originally Posted by Plummit

...
BTW, the original builder of my plane told me that the QB tanks leaked "like a sieve" from the very beginning. I have no reason to dis-believe him after the stories I've read from other QB builders.

-Marc

Why didn't the original builder pressure test the tanks and fix the leaks before putting them in service, is what I would want to know.

[Flandy10]

Just because there are persistant tank leaks being repaired, I wouldn't automatically assume the rest of the build is questionable. It depends of which rivets were leaking.

The RV-10 tanks are the only ones in the fleet (I think) that have stiffeners on the inboard bay. It doesn't matter if they were built perfectly, because if you sit or step on them enough, you WILL break the seal on the end rivets on the stiffeners. **Ask me how I know. **

There are four stiffeners in the inboard bay. The forward is significant because it is the tank attach point. The third back from the front is a J-channel that runs the length of the tank. It is the unsupported end of the J-channel and the other two that are the problem. They are attached to the skin only and will flex everytime you put any pressure on them. Eventually, you will break loose the proseal on the end rivets of these stiffeners. Green locktite will not keep these from leaking- been there, done that. The only thing that will is NEVER allow anyone to step forward of the wing spar- good luck with that.

It would have be nice if Vans had connected these three stiffener ends to the rib but that is another story.

**(I've had both tanks off at least once to repair these leaks and the last time I made a modification that tied them to the rib- one year later--no leaks)