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Proseal turning to goo

cropdusterdave

Well Known Member
I'm sure it's been discussed before...but I've only been able to find limited info. I've had my RV-7 flying for about a year and a half now. The left wing tank had a minor leak when the tank was full that I decided to leave until the annual. In the meantime...if fuel sloshed around and after flying...I'd have to clean up some blue stains. So at the annual, I pulled the tank...identified the leak....fixed...and reinstalled the tank. I was out of town for the next few months for a work commitment during which time I left the tanks dry. A couple weeks ago...I filled that tank up and all looked good. The next week.....leaking again. Worse than before. So off comes the tank again. The pro seal on the outer rear surface (where it attaches near the spar) has turned to goo. I can scrape it off with my fingernail. It's also turning kind of a green color.

So from what I could dig up for info on this...is that pro seal that has been exposed to periodic fuel wetting and oxygen can do this. Peeking inside the tank and feeling around with a screw driver tip....the pro seal inside does not appear too be gooey at all. I don't know weather to assume that the tanks are a write off as all of the pro seal is failing.....or if I can fix this by removing and replacing the affected external pro seal areas.

In the same tank...a single rivet on the bottom surface has begun to weep as well. Don't know if this is common in a recently completed aircraft...or if this is another symptom of failing pro seal.

Any insights that you good folks might have would be very appreciated! I'll be gutted if my tanks are trash. But if they are....might as well get going on the next steps.....
 
definitely

Yes, the ProSeal will definitely do this, particularly if a small leak or seep, no matter how tiny, is not fixed immediately. The unresolved leak or seep will turn the ProSeal to peanut butter, and the problem will only worsen with time. Remove all ProSeal that is not firm, redo it, and be sure you fix the initial seep. Pressure test. Use fresh ProSeal, mix carefully, let it cure a couple weeks.
See this thread, for one:
http://www.vansairforce.com/community/showthread.php?t=164892

I fixed mine myself, successfully. There is a product, both liquid and gel, that will supposedly eat away all the bad ProSeal for you. I tried both gel and liquid, and was not that impressed with its performance. I used acetone, plastic scrapers, plastic fiber wheels, Scotch-Brite, and lots of elbow grease, and got mine all cleaned up nice.

There's also a company that will do it for you, but it's pretty expensive:
Paul Beck
Weep No More/Oasis Aero
320-295-1671
weepnomorellc.com

Your tanks are not trash, but any with any seep at all needs to be cleaned up and fixed.
 
Last edited:
Paul Beck....Weep No More

I can vouch for Paul and the service that he provides. Yes, it?s pricey, ($1200/per tank) but you?ll never have another leak after he?s done his magic on them. He removes the rear of the tank, completely strips the inside clean, applies his sealant, and re-assembles the tank. I went ahead bit the bullet on my new -7 build and did a preemptive strike on my tanks that came with the quick-build kit and had him open them up to do his treatment on them. He told me that the quality of the sealant job that he observed on my quick build tanks was very poor and that it would have been very likely that I would have experienced leakage. Paul is a heck of a nice guy and very honest and I highly recommend him and the service that he provides.
 
Thanks for the info guys! I appreciate the link to previous threads addressing the issue. Looks a lot more common that I realized. So I think my plan off attack will be: Purchase the fuel tank repair kit from van's which will allow me to inspect the internal pro seal. If all is good in there....as it has been for many others...I'll remove and replace the exterior sealant. If it is bad? God I hope it's not...then I'll have some decisions to make. I've been trying to get a hold of Paul...he must be busy.
 
From what I saw on mine and heard from others' descriptions, it generally tends to be the outer ProSeal that turns to goo, which makes fixing it yourself feasible. Fortunately, on mine, the initial seep was pretty much right under the fuel access hole, so I laid the ProSeal on lavishly in there, too, when I cleaned and redid the outside. The only parts on the outside that needed it were where any fuel seepage had gone. so it seems to be an out-of-tank phenomenon.
 
...I'll remove and replace the exterior sealant. If it is bad? God I hope it's not...then I'll have some decisions to make. I've been trying to get a hold of Paul...he must be busy.

Tank leaks need to repaired from the inside, applying sealant to the outside is not the way to fix a leak.
 
Not to beat a dead horse, but I had the same issue twice in my 27 year old RV4. It had a leak when I bought it in 2012, in 2015 during annual we took the tank off and it was gooey in the same spot you described. We removed and replace the tank. I noticed about 2 months ago a seep, so I took the tank off and the same spot was gooey again down to the rivet on the bottom you described. I did use some Pro Seal remover, but acetone, scotch pads, scrapers time and effort is what you end up doing. Re-applied fresh Pro Seal (get new) and let cure, past the leak test, but am letting set for a month (while waiting on a prop re-finish). I wouldn't junk the tank, just rework it.
 
I agree but....

Tank leaks need to repaired from the inside, applying sealant to the outside is not the way to fix a leak.

It's interesting that Van's told me I could put proseal on the exterior of the leaking rivets on top of my tanks to repair. That's counter-intuitive to what I know about leaking things.

-Marc
 
It's interesting that Van's told me I could put proseal on the exterior of the leaking rivets on top of my tanks to repair. That's counter-intuitive to what I know about leaking things.

-Marc

My plane was 2 years old when a small leak started on the upper side of the inboard most rib. I cleaned the area and scoured with scotch-brite and put pro-seal on the region of interest. I did not remove the tank to do this. No leak 16 years later. So, yes, at least some leaks can be successfully fixed from the outside.
 
Well I just ordered 5 of the tank repair kits from Van's. I don't want to be monkeying around with this for years....so may just as well open it up and re-work that aft plate area. That'll allow me to get to that one weeping rivet also. If I don't....I'll always be worried about a follow-on leak.
 
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