Frustrating Fuel Leak(s). Is It Possible That...

[pilot_jb]

Guys, I need some help here. I’ve been chasing a leak in my right tank since last year and I’m a bit baffled, because it’s now moved in a major way. 
 

Last year, my IA and I sealed a leak which was showing along the bottom of the right spar in the gear well. We got it, but not completely. We’re in MI and it may or may not be important that it started after it got cold. After it got cold this year the same leak became worse, so we went back in. I found the internal leak location using Don’s soap and vacuum method and repeated this process each time (twice). Since the internal leak was at the top of the spar right behind the middle access panel on the top of the wing, I think we just missed it the first time. This area is really tight and we were much more liberal with the sealant last year, because we waited to reseal the access panel. This will make sense to those of you who have done it. After repairing the leak a few weeks ago, the wing was completely dry, and the plane sat through several cold/warm cycles of weather. 
 

Today, I flew the plane for the first time since the latest repair. On base, about .5 hours into the flight, I got a heavy fuel scent in the cabin. I pulled up to the pump, got under the wing, and now she’s leaking heavily into the leading edge. By heavy, I mean pooling. 
 

I didn’t look inside the leading edge before the flight, but I’m confident that it wasn’t leaking from the front until sometime during the flight, and the front of the right side was never a problem. 
 

My question is this...is it possible that the tank is being pressurized, likely though the vent tube, in flight?  It doesn’t make sense that the back is no longer leaking, but the front is now has a running leak, and during the first flight after being dry on the ground for several weeks. It seems to me that something is pushing the fuel past the seams. 
 

Is there a one way valve in the fuel vent that may be stuck open?  
 

Thoughts?  This is getting frustrating to the point that I’m thinking about selling my beloved F. 

[Niko182]

41 minutes ago, pilot_jb said:

Guys, I need some help here. I’ve been chasing a leak in my right tank since last year and I’m a bit baffled, because it’s now moved in a major way. 
 

Last year, my IA and I sealed a leak which was showing along the bottom of the right spar in the gear well. We got it, but not completely. We’re in MI and it may or may not be important that it started after it got cold. After it got cold this year the same leak became worse, so we went back in. I found the internal leak location using Don’s soap and vacuum method and repeated this process each time (twice). Since the internal leak was at the top of the spar right behind the middle access panel on the top of the wing, I think we just missed it the first time. This area is really tight and we were much more liberal with the sealant last year, because we waited to reseal the access panel. This will make sense to those of you who have done it. After repairing the leak a few weeks ago, the wing was completely dry, and the plane sat through several cold/warm cycles of weather. 
 

Today, I flew the plane for the first time since the latest repair. On base, about .5 hours into the flight, I got a heavy fuel scent in the cabin. I pulled up to the pump, got under the wing, and now she’s leaking heavily into the leading edge. By heavy, I mean pooling. 
 

I didn’t look inside the leading edge before the flight, but I’m confident that it wasn’t leaking from the front until sometime during the flight, and the front of the right side was never a problem. 
 

My question is this...is it possible that the tank is being pressurized, likely though the vent tube, in flight?  It doesn’t make sense that the back is no longer leaking, but the front is now has a running leak, and during the first flight after being dry on the ground for several weeks. It seems to me that something is pushing the fuel past the seams. 
 

Is there a one way valve in the fuel vent that may be stuck open?  
 

Thoughts?  This is getting frustrating to the point that I’m thinking about selling my beloved F. 

I think at this point its time for a visit to florida or minnisota for a reseal. Seems like youre just chasing leaks. I believe to reseal 1 tank is right around 4k. That comes with a 7 year warranty too.

Edited December 25, 2019 by Niko182

[Immelman]

I am not an expert having only done a couple of patch jobs, chasing one pesky leak, but I do remember how frustrating the whole ordeal is if you open, patch, wait, seal, fuel and it leaks again. Very frustrating indeed.

If you used the maxwell method, I presume you applied vacuum to the fuel vent. To my knowledge those are not one way valves, just vents, air should be able to flow in both directions.

I am very much a proponent of patching leaks vs reseal but perhaps it is time to completely redo your right tank? If you're in MI you're not nearly as far from MN....

[Yetti]

I believe the conventional wisdom is that walking on the wing walk causes leaks up on the leading edge.

[carusoam]

Considering how vents work...

If the vent gets plugged... while fuel is being removed... the tank goes under vacuum... and the sheet metal starts to oil can visibly from the outside...

What does your fuel tank vent look like? Most are a tube inside a pipe that allows air into the tank... if the tube has been altered into the shape of a pitot tube... then some pressure may be being forced into the tank...

Question... how much pressure is required to cause a leak?   Probably a lot...

One flight, and a leak opens up...  that is worth looking into to see what didn’t hold after all the work you got accomplished...

fuel aromas based on bank angle can be a bit misleading... as in you flew with perfection, keeping the ball centered... but one moment later... a slight ball off centered / wing high... you might get fuel rushing towards the cabin... causing the aroma noticed by the pilot...
 

Or is the old sealant just not holding up?
 

Some sealant was bad when it was installed the first time.... most of it was improved after the 90s.... Today, tank stripping and sealing are more of a science than an art...

If considering putting patches on top of patches... also consider stripping the tanks and starting over...

PP thoughts only, not a mechanic...

 

Best regards,

-a-

[0TreeLemur]

On a big cross-country in the summer of 2018, from Alabama to Utah and back, our slightly leaky on both sides C became a 1 gallon overnight leak from one tank.  It just happened.   We had our tanks re-sealed last Oct. and despite the cost, have been happy with the results.   No leaks.  No fuel smell.  No worries.

[S.C.]

I’m seeing a leak problem on my left wing. A&P just quoted me $10,000 and he’s not sure he can get the parts.  What are the other options and do you think it is worth doing both tanks at once.  Any advice or alternatives are appreciated.

 

Thanks,

Steve

[Skates97]

10 minutes ago, S.C. said:

I’m seeing a leak problem on my left wing. A&P just quoted me $10,000 and he’s not sure he can get the parts.  What are the other options and do you think it is worth doing both tanks at once.  Any advice or alternatives are appreciated.

 

Thanks,

Steve

More information/pictures? Where is it leaking, how much?

[Oldguy]

13 minutes ago, S.C. said:

I’m seeing a leak problem on my left wing. A&P just quoted me $10,000 and he’s not sure he can get the parts.  What are the other options and do you think it is worth doing both tanks at once.  Any advice or alternatives are appreciated.

 

Thanks,

Steve

Wow! I would check with Houston Tank Specialists, LLC down in Eagle Lake. For that figure you can probably get both tanks stripped and resealed. It is probably less than 45 Mooney minutes to get there from San Marcos.

They have always been good to the Mooney pilots and support the Mooney Summit. Give them a shout.

[cferr59]

21 minutes ago, S.C. said:

I’m seeing a leak problem on my left wing. A&P just quoted me $10,000 and he’s not sure he can get the parts.  What are the other options and do you think it is worth doing both tanks at once.  Any advice or alternatives are appreciated.

 

Thanks,

Steve

What parts?  I have a feeling it might be a good idea to get a second opinion.

[kpaul]

14 hours ago, S.C. said:

I’m seeing a leak problem on my left wing. A&P just quoted me $10,000 and he’s not sure he can get the parts.  What are the other options and do you think it is worth doing both tanks at once.  Any advice or alternatives are appreciated.

 

Thanks,

Steve

10K to fix a leak?  the two Mooney tank specialist shops quote about $7800 for a complete strip and reseal of both wings and that is with a 7 year warranty.  A complete set of Griggs/O&N bladders is $9000 + install.  I think your A&P is actually telling you he does not want to do the job. 

Actually I see you have a C, your cost would probably be slightly less. The prices I gave are for the 64 Gallon mid body planes.

[Niko182]

Id suck it up and fly to MN to get the tanks resealed. Do it once and dont deal with anything for at least another 10 years.

 

Edit:in my opinion its always quite fun doing the really long XC flights to when getting an aircraft or sending it somewhere for a big repair. Spend 2 or 3 days flyong over a large chunk of the US and possibly a different country. Then it all sucks when you gotta be cramped in an economy seat for 4 or 5 hours on the way back and thats when you realize how much you really love your personal airliner. Picking my plane up from wisconson and flying it back to california was probably one of 3 flights where i learned the most about being a pilot. If i need to fly 5 to 8 hours and a couple days to drop the plane off, itll usually be a really good experience so i dont mind it.

[DonMuncy]

1 hour ago, S.C. said:

I’m seeing a leak problem on my left wing. A&P just quoted me $10,000 and he’s not sure he can get the parts.  What are the other options and do you think it is worth doing both tanks at once.  Any advice or alternatives are appreciated.

 

Thanks,

Steve

Call and talk to Carl, at Houston Tank Specialists.

[nfonville]

I used Paul at Weep No More in MN on my 201 about 10 years ago.  I was very happy with the service and scheduling. I highly recommend Weep No More.

 

[EricJ]

If it's just a leak and can be patched, which most leaks can, it can be likely be done for less than $1k.   Maxwell's shop in Longview, TX, successfully patched mine for $600 a few years ago.

 

Edited January 23, 2020 by EricJ

[carusoam]

This is why pics are so important...

Some leaks only require replacing things like a rubber tube, or a gasket.... or re-torquing screws properly...

I got to talk with Carl Sharon from Houston Tank at the Summit...

It is a great conversation if you are considering stripping and resealing...
 

Best regards,

-a-

[S.C.]

Thanks for all the great leads!  I was sweating it.  I had to replace the mains last annual and was worried that this was going to ruin my flying plans.

[S.C.]

Also, for those who requested pictures, I’ll be sure to send them next time.  I’m away from home this week and haven’t been able to assess myself yet.  Again, Thank you all so much for the suggestions.  
 

Steve

[Htwjr]

I patched my C with my a&p's supervision a couple of years ago using Maxwell's method.  I also took the time to strip the old sealant from anywhere close to where the leaks were before applying the new sealant as I did not want to just put good sealant on top of bad.  I have been flying for two years from a grass strip with no leaks since.  When my tanks do need a total strip and reseal I will take it to one of the professionals as the patch job was enough work for me.  Its hard to beat a man at his own game.