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Ahhh… Fuel Tank leak! Next steps?

WingnutWick

WingnutWick

Well Known Member
So I had just had a nice long run with nothing going wrong with the planes and I made the mistake to have the sabatoging thought “wow, it’s been quite some time since anything has gone wrong with the planes!” and that’s when I knew I messed up. Sure enough next flight P-Mag failed its internal power check on the 10 and just yesterday while airing up a tire on the 8 I see blue streaks of fuel seepage on the bottom of the wing spanning the length of the tank seam. I peeked around and couldn’t see any leakage from fuel tubing, and bore scoping behind the tank showed blue fuel witness marks and a little dark spots of un-evaporated fuel lining the back of the tank (as expected from the seepage in this photo).

So, first off - how much of a pain of a fix is this? Secondly - what are the steps to fix this? I need to assess if this is a me project or a throw money at the problem project.

Thanks all!

WN
 
WingnutWick said:
So I had just had a nice long run with nothing going wrong with the planes and I made the mistake to have the sabatoging thought “wow, it’s been quite some time since anything has gone wrong with the planes!” and that’s when I knew I messed up. Sure enough next flight P-Mag failed its internal power check on the 10 and just yesterday while airing up a tire on the 8 I see blue streaks of fuel seepage on the bottom of the wing spanning the length of the tank seam. I peeked around and couldn’t see any leakage from fuel tubing, and bore scoping behind the tank showed blue fuel witness marks and a little dark spots of un-evaporated fuel lining the back of the tank (as expected from the seepage in this photo).

So, first off - how much of a pain of a fix is this? Secondly - what are the steps to fix this? I need to assess if this is a me project or a throw money at the problem project.

Thanks all!

WN
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Empty the tank, pull the tank, pressure test it and apply soapy water until you locate the source of the leak(s). My -10 tanks (built by the guy I bought the 2nd hand kit from) had a leak at the aft baffle seam. It was in the same bay as the fuel fill cap and I was able to apply type A proseal through the opening to problematic area without further disassembling the tank. You may be similarly lucky. Or maybe not. That's when you'll know how to proceed. If you can't access the leak without some sort of disassembly, the best path forward is probably to cut an access hole in the appropriate bay in the rear baffle and fix the leak through that hole. You could probably do it in an afternoon or two if you were serious about it.
 
WingnutWick said:
I did not.
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If it is the back "baffle" (the rear of the tank) leaking at the joint to the lower skin, and if the leak spans across more than one rib (bay)... then I'd recommend the whole back baffle be removed. That involves a TON of rivets on the top and bottom. Just had mine done by Steve Barnes (noted above) and recommend that route.

If it is local to one bay, then you may have luck using the Vans tank patch / access panel. It involves opening a hole in that one bay via the back of the tank, and unfortunately working by mirror and feel.

Option A is going to mess up the paint. Option B won't.

I noted your location... at least you are within easier drive distance to Steve. I needed to ship. The RV6 19 gallon tanks barely can be fit into a non-oversize box. Oversize caused the shipping rate to double (close to $500 one way from S. Cal to N. Cal).
 
I just went through this on my RV9A. Leak was at the rear baffle between the first and second bay (first being closest to the fuselage). It was also leaking at the bottom corner back baffle quite a bit. I accessed the first bay through the fuel sender/fuel pickup access panel and cut a 5" hole for access to the second bay and closed with Van's tank patch kit cleaned off all the pro seal on the lower baffle in both bays. scuffed up the aluminum and resealed with flame master chem seal CS3204 B2. I didn't build the plane or tank. did a bunch of research on these forums and went for it. It was time-consuming but not really hard. I ended up curing the tank in my bathroom for 3 days just to make sure. It's completely leak free now. below is a picture of my 'bathroom curing box'. You can see the vans patch on the second bay.
 

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FWIW - I ordered a patch panel from Vans and got hung up in the RV15 kit shipping. I got frustrated and so I designed my own patch panel, sent the design to SendCutSend and got it promptly. If anyone wants, I can provide you the dxf file so you can order you own.

I bring this up as I see RV15 tail kits are about to ship....
 
I've done a bunch..these were severely leaking -4 tanks, I cut open each bay, cleaned and resealed. I make my own plates, buy the closed end rivets by the 100's from ACS. 1422B1/2 for the fillet seal inside and tank plate fay surface close, 1422A1/2 for the smooth brush on topcoat of all access panels and rivet lines externally. Butter the plates fay on both surfaces for best adhesion, cleco 100% and let set 10 min, then pull a cleco/install a rivet one at a time.
 

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Hey folks. I too discovered a leak and I'd like to speak to Steve about a repair. I'm in the SF Bay area and could drive one/both up. I'm curious about turnaround time, cost, etc. I din't build my tanks (nor my plane) so not sure this is a job I can do...
 
donmtt said:
Hey folks. I too discovered a leak and I'd like to speak to Steve about a repair. I'm in the SF Bay area and could drive one/both up. I'm curious about turnaround time, cost, etc. I din't build my tanks (nor my plane) so not sure this is a job I can do...
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Is it a rivet or two, or worse? Pics?
Steve likes to pull the whole back of the tank off and do it all right. Clearly not cheap, although he is a good value.
If it is a couple rivets there are possible alternatives.
 
blaplante said:
Is it a rivet or two, or worse? Pics?
Steve likes to pull the whole back of the tank off and do it all right. Clearly not cheap, although he is a good value.
If it is a couple rivets there are possible alternatives.
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Thanks. I'll have to try to get in with my borescope to see....All I see now is dark blue stains and liquid fuel along the aft lower seam on the right tank. FYI, the problem came to my attention over the last couple of weeks. I keep my canopy closed in the hangar and I'd go out to fly and the fuel smell was borderline overwhelming when I'd slide the canopy back. Unfortunately, as I was digging in this week I found a leaking brake line and fixing that has led to myriad other issues...
 
donmtt said:
Thanks. I'll have to try to get in with my borescope to see....All I see now is dark blue stains and liquid fuel along the aft lower seam on the right tank. FYI, the problem came to my attention over the last couple of weeks. I keep my canopy closed in the hangar and I'd go out to fly and the fuel smell was borderline overwhelming when I'd slide the canopy back. Unfortunately, as I was digging in this week I found a leaking brake line and fixing that has led to myriad other issues...
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Also, regarding that approach of pulling the back of the tank off, isn't that gonna involve paint work as well?
 
donmtt said:
Thanks. I'll have to try to get in with my borescope to see....All I see now is dark blue stains and liquid fuel along the aft lower seam on the right tank. FYI, the problem came to my attention over the last couple of weeks. I keep my canopy closed in the hangar and I'd go out to fly and the fuel smell was borderline overwhelming when I'd slide the canopy back. Unfortunately, as I was digging in this week I found a leaking brake line and fixing that has led to myriad other issues...
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If you smell fuel please "Stop" flying.
 
donmtt said:
Also, regarding that approach of pulling the back of the tank off, isn't that gonna involve paint work as well?
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Depends. If the tank and all the attach screws were in place when the plane was painted... then probably will damage it getting it off.
If they (hopefully) had the screws partly out, or painted the tank separately, then no.

Since you can't see the weeping rivet, and it could well be a seam... the tank has to come off to evaluate.

Just went through all this on my plane. Quick build tank that per Steve Barnes had very insufficient amount of sealant used in assembly. Before I turned it over to him I had a look and completely agree with his assessment.
 
donmtt said:
Also, regarding that approach of pulling the back of the tank off, isn't that gonna involve paint work as well?
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Yes. That is the way i do it. It is much easier to do a thorough job when the rear baffle is off. I usually tape up a 1” strip for the paint remover on the rivet lines so a bit easier for the paint repair. You can cut a bunch of holes in the baffle, but much more difficult access. To do it right, you want to strip all the old stuff off and that is a lot harder via holes. It is bad enough you ate doing this with mirrors; limiting access just makes it a lot harder to do right.
 
donmtt said:
Thanks. I'll have to try to get in with my borescope to see....All I see now is dark blue stains and liquid fuel along the aft lower seam on the right tank. FYI, the problem came to my attention over the last couple of weeks. I keep my canopy closed in the hangar and I'd go out to fly and the fuel smell was borderline overwhelming when I'd slide the canopy back. Unfortunately, as I was digging in this week I found a leaking brake line and fixing that has led to myriad other issues...
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If you have noticeable staining, you need to go inside and remediate. Very unlikely to be just a rivet.
 
There are many leaky fuel tank threads on VAF. To the point where there should be a permanent category devoted to this subject.

Sad stat - of the 60 customer RVs that have gone through my shop over the years, 11 (20 tanks) had fuel tank leak issues requiring removal, opening up & re-sealing. 4 of these tanks required TOTAL rebuilds. Not a good ratio…

Satisfying stat (so far) - tanks on all my personal RV builds are solid to this point, oldest one 21 years flying. I was sure to be quite generous with the Proseal during their builds.
 
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