Loose rivets causing seeping fuel?

[par]

I should have taken some picture but unfortunately I didn't. So, I'll do my best to describe the issue and grab some pictures this weekend. I have had seeping fuel from the right tank up in the forward part of the main wheel well since I bought the plane. Two different mechanics have not attempted to reseal this area but the fuel keeps seeping out. The first mechanic was straight up shitty so I wasn't too surprised by his work but I believe the mechanic I am currently working with knows what he's doing. After discussing the issue with him today, he thinks it could be loose rivets that run along the length of the tank bottom. To my untrained eye, I think he is correct because that's where I see the fuel seeping out. He wants to replace all the rivets in this area and says it should solve the problem. 

 

Have any of you ever come across this issue? I am being told that you can test for loose rivets by attempting to twist them with vice grips. If they spin easily, the answer is obvious. At this point, I just don't understand what else could be causing the issue. 

[carusoam]

Typically, loose rivets leave a gray trail behind them...

This effect is called smoking rivets. It looks like they have left a smoke trail.

Fuel is so low in viscosity, it can leak through rivets that are tight. Rivets in the fuel tank are sealed with a rubbery sealant.

My 65 C had lots of smoking rivets in its old age. And lots of fuel leaks not related to the rivets.

The nice thing about leaking rivets is, they are a single point problem that can be easily identified and repaired by a mechanic following a procedure.

Do you have smoking rivets? Are they in the fuel tank areas?

Best regards,

-a-

[N33GG]

Don't feel special, you're not the first to have leaking rivets. Very common problem. Some Mooney owners have been flying with them for years. Some owners want them fixed at the first sign. Which kind of owner are you?

[par]

Typically, loose rivets leave a gray trail behind them...

This effect is called smoking rivets. It looks like they have left a smoke trail.

Fuel is so low in viscosity, it can leak through rivets that are tight. Rivets in the fuel tank are sealed with a rubbery sealant.

My 65 C had lots of smoking rivets in its old age. And lots of fuel leaks not related to the rivets.

The nice thing about leaking rivets is, they are a single point problem that can be easily identified and repaired by a mechanic following a procedure.

Do you have smoking rivets? Are they in the fuel tank areas?

Best regards,

-a-

 

I don't know if I have smoking rivets. After googling for some pictures, it appears you would need the rivets to be in the air stream to have the smoking effect. These rivets are located in a spot where the air stream will never touch them. I am really wishing I had taken some pictures last weekend.

[par]

Don't feel special, you're not the first to have leaking rivets. Very common problem. Some Mooney owners have been flying with them for years. Some owners want them fixed at the first sign. Which kind of owner are you?

 

I would like to eliminate the slight smell of fuel in the cockpit so I guess i'm the latter type.

[RobertGary1]

Smell in the cockpit is likely the inner fuel sender seal.

-Robert

[carusoam]

Smoking rivets are definitely outside. If you don't have any outside, it would be less likely? To have them inside.

For the inside fuel aromas, check the seals for the fuel level senders. They are the prime culprit. Original seals were made from cork sheets.

Removal of the interior side panel may be required. Relatively easy to do.

If you have blue stains on the carpet in the back seat to match the aroma, this is a big hint to get something fixed.

Newer Mooneys have two level sensors per tank.

This is from my 65C experience. My R experience had leaking rivets on the top of the wing when I got her. The PPI identified and fixed them.

Of all things, these were low cost fixes that are best to take care of as soon as they are identified. MS hadn't got started for another year after my C ownership.

Best regards,

-a-

[par]

Smell in the cockpit is likely the inner fuel sender seal.

-Robert

 

It was...had both rebuilt and they are no longer leaking. The carpet is completely dry and I haven't been able to detect any visible fuel anywhere in the cabin.

 

Here is my theory: The seep is making its way along the bottom of the wing to the belly where it appears to go inside one of the belly panels. Its a extremely faint smell but I can def smell it after I land and open the door/window. Can the carpet continue to smell after a leak permanently? Much of it was soaked with fuel before rebuilding both fuel senders. 

[Piloto]

A leak may not be coming from inside the tank rivet part but from along the rib from another leak point. Best way to find the leak point is by pressurizing by mouth the tank and looking for air bubbles on the outside with a foamy cleaner like SD-20. The tank must empty for this test.

 

José 

[Raptor05121]

Drop the belly panels and look at the lower tank seam. The plane I just pre-purchased yesterday has this problem. IA says it can be sealed

[RobertGary1]

As long as there are no systemic problems with the sealant (widespread cracking, peeling) you can always spot seal.

-Robert

[HRM]

I should have taken some picture but unfortunately I didn't. So, I'll do my best to describe the issue and grab some pictures this weekend. I have had seeping fuel from the right tank up in the forward part of the main wheel well since I bought the plane. Two different mechanics have not attempted to reseal this area but the fuel keeps seeping out. The first mechanic was straight up shitty so I wasn't too surprised by his work but I believe the mechanic I am currently working with knows what he's doing. After discussing the issue with him today, he thinks it could be loose rivets that run along the length of the tank bottom. 

 

I don't think your problem is rivets, although loose rivets could be exacerbating the real problem.

 

Mooney tanks are sealed with a rubberized coating and their integrity is not wholly dependent on the tightness of the rivets.

 

How are the loose rivets going to be tightened? Tapped on with a hammer while bucked from behind? Drilled out and replaced?

 

Either of those approaches will destroy the sealant integrity.

 

Since you have been through two A&Ps who are obviously not experts on Mooney fuel tanks, I recommend you send photos to Paul Beck at Weep No More and get his opinion.

 

I am certainly no expert, but my guess is that you need that tank resealed, but first it needs to be stripped, then the rivets tidied up or replaced.

 

Opinions are like belly buttons, everybody has one 

[RobertGary1]

When you replace a wet rivet you need to coat it with some sealant. To get behind them you'll need to open a wet access panel. That will need to be resealed with an "access panel" sealant. Don't use regular B-2 on the access panels or you'll be cursed forever by the next person who needs access. None of this is beyond the ability of an owner to do with proper supervision. An A&P will need to sign off, additionally there is an AD that must be signed whenever sealant is applied. 

 

-Robert

[N201MKTurbo]

The place you describe is a common place for stains to show up.

I doubt you have a rivet problem, you just need to fix the leak.

In reality you could remove all those rivets and seal the tank. (Don't fly it like that) Even if the rivets were loose, it would require a failure of the tank sealant to cause the fuel leak.

[Browncbr1]

I started to smell a little fuel in the cabin when opening the door after a day or two... I knew that it had been about 12 years since my right tank had last been sealed... I also have a few small dots of dye under the wing.... A friend suggested I check the screws on the sender, so I pulled the interior panel off to see that there is a leak at the aft root... It appears that at some point, the previous owner had a leak here that was patched externally... It seems the patch is starting to give way now... 

 

For you, I hope it is just the fuel sender screws that can be tightened...  For the attached problem, it looks like I will be in for a little more detailed and costly remedy....   During the summer, it's ok, as I have all vents open, but I don't want to go into Fall and Winter with this problem.  It seems to be coming from the bottom seam and/or rivets...  sealant is gooped all over it..   All of the dye you see is actually under sealant.. 

 

 

[Sabremech]

Hi Robert,

 I'm not aware of an AD that needs to be signed off each time the fuel tanks require sealant being applied. Are you referring to AD 85-24-03? If so, this was a one time AD the way I read it.

 Thanks,

 David

[nels]

Would you need to replace rivets? Wouldn't re bucking them work? In any case, it seems like tightening up the existing rivets would be a good thing to do prior to a reseal.

[RobertGary1]

Would you need to replace rivets? Wouldn't re bucking them work? In any case, it seems like tightening up the existing rivets would be a good thing to do prior to a reseal.

 

I'd  coat them with some B-2 before bucking them if they are wet rivets. 

 

-Robert

[mike28w]

  My 2 cents....   I'd double check to make sure that there are no leaks around those senders.

 

I'd also make sure that the mechanic had done a very thorough job of cleaning up the residue from the previous leaks.  I suspect that you may be smelling residue.   Are your carpets easily removed ?  If so, I'd remove them and then go for a ride.

 

Not speaking from experience , just my opinion.  Good luck...mike

 

 

It was...had both rebuilt and they are no longer leaking. The carpet is completely dry and I haven't been able to detect any visible fuel anywhere in the cabin.

 

Here is my theory: The seep is making its way along the bottom of the wing to the belly where it appears to go inside one of the belly panels. Its a extremely faint smell but I can def smell it after I land and open the door/window. Can the carpet continue to smell after a leak permanently? Much of it was soaked with fuel before rebuilding both fuel senders. 

[mike28w]

Hello to Par !

 

  Just curious if you've found out anything more about your problem ??  If you do , please let us know....any info on Mooneys is valuable !

 

Thanks, mike

[pinerunner]

I wouldn't grab onto a rivet with a vice grip and twist. Aluminum is a relatively soft metal and I'd be afraid of messing up perfectly good rivets. Rivets that loosen up tend to show a dark ring through the paint job. I think the ring has fine aluminum particles formed as the loosening rivet "works" against the skins it was holding together. It'll usually easy to spot a loosening rivet fairly early. If they're REALLY loose you can wiggle them with your finger.

 

Bucking a rivet is basically a one time thing; if it goes bad you should drill it out and start fresh. A rivet kind of flows and changes shape to fill the hole and subjecting it to multiple iterations of this invites metal fatigue. Any way they're cheap. I'm not a mechanic but my dad was and I bucked maybe a thousand rivets in his multiple rebuild projects so I have a clue.  Some (most?) of my opinions are kind of second-hand I'll admit.

 

Some leaks can originate from a very different location inside the tank than where you see it on the outside. Don Maxwells website has a great description of how to find them. Just google Don Maxwell and leaks and you'll find 

 

http://www.donmaxwell.com/publications/MAPA_TEXT/_overlay/Fuel%20Tank%20Repair_How%20We%20Fix%20Them%202-05.htm

 

 

[sleepingsquirrel]

I have a Mooney manual and it says a leaking rivet can be re struck once. I have two or three that lost their heads and I have temporarily stopped the leak with an external patch with sealant. I hear Loctite 290 can be sucked into a leaking rivet with a slight vacuum on the tank. It really sounds that the sealant in the tank is giving up the ghost.