B

Ben Witmer

I'm New Here
My RV-12 was finished in the spring of 2012 . I now have 80 hours in it and
my fuel tank has developed a leak caused by a deterioration in the pro seal .
Does anyone else have the problem ? Does the ethanol in mogas cause it?
If I reseal will the problem reoccur ?
Thanks,
Patrolsky
 
fixing a leak

I use mogas with ethanol in my RV7A (with a Subaru engine) and have no issues with it affecting the proseal (over 5 years old now).

Why do you say it is due to a deterioration of the proseal?

I have repaired a leak in one of my tanks, due to improper coverage during the build. I cut access holes, resealed with proseal, and sealed up the access holes and have had no issues since.
 
Ben Witmer said:
My RV-12 was finished in the spring of 2012 . I now have 80 hours in it and
my fuel tank has developed a leak caused by a deterioration in the pro seal .
Does anyone else have the problem ? Does the ethanol in mogas cause it?
If I reseal will the problem reoccur ?
Thanks,
Patrolsky
Click to expand...

Ben, could you tell us where the leak is located and how bad it is?
I tend to agree with Dennis, if proseal was prone to deterioration I would not think VANS (or anyone else) would recommend its use. It is critical that you find the mode of failure by inspecting the tank from inside to find out what happened. I had a leak through a rivet hole in which the shank had departed. I was lucky that this happened before I ran the pressure test but it could as well have happened after the tank was put in service.
 
Crawley,

My question was not directed at the Pro-seal. The tight quarters around the fuel tank have made me reluctant to remove it for fear of disturbing a seam. Others have discounted that concern, but I remain unconvinced. I asked the question to see if handling the tank during routine removal may have been a contributor to springing a leak.

Rich
 
RV-12 Fuel tank leak

My tank is out of the plane but we have not looked inside yet.
The leaks are along the rear seams , about 1/2 gal a day.
Deterioration was suggested because the pro seal feels spongey or
tacky. My builder mixed the sealant as per instructions.
Does the unmixed proseal have a shelf life ?
Thanks for your help,:mad::mad:
Ben
 
Ben Witmer said:
My tank is out of the plane but we have not looked inside yet.
The leaks are along the rear seams , about 1/2 gal a day.
Deterioration was suggested because the pro seal feels spongey or
tacky. My builder mixed the sealant as per instructions.
Does the unmixed proseal have a shelf life ?
Thanks for your help,:mad::mad:
Ben
Click to expand...

This was not caused by ethanol fuel.

When sealant is kept constantly wet with fuel because of a seep/leak and in an environment that provides an oxygen source (on the outside of the tank) it can turn the sealant into goo.
 
pro seal life

yes it does have a shelf life it will be marked on the container from memory it doesn't have a long shelf life
one possible cause of a leak is that there may have been a void or a section which was only just sealed and over time and movement etc this section has started to leak ie if there was only a very very thin layer over a rivet it would seal for a while but wouldn't take much to cause a leak
 
moving tank

RFSchaller said:
Crawley,

My question was not directed at the Pro-seal. The tight quarters around the fuel tank have made me reluctant to remove it for fear of disturbing a seam. Others have discounted that concern, but I remain unconvinced. I asked the question to see if handling the tank during routine removal may have been a contributor to springing a leak.

Rich
Click to expand...

yes I believe handling a tank could cause a leak
 
I have a friend who is a retired fighter pilot. He said the F-4 tanks were notorious leakers that were fixed by pumping sealant into the screw holes and then replacing the screws. He said the joke in his squadron was there was probably more sealant than fuel in the tanks.
 
crashley said:
yes I believe handling a tank could cause a leak
Click to expand...

Sure.
If you drop it (and cause visible damage) while handling it, but short of that it is highly unlikely.
90 pounds of fuel (15 gal) sloshing around inside is going to apply more localized load than handling it will.
 
Scott,

Does your conclusion apply to the de-torquing and retorquing of lines at the fittings on the bottom? I recall a thread saying that applying counter torque is difficult and it is possible to develop a leak between the tank and the fitting.

Rich
 
oxygen in the fuel tank

rvbuilder2002 said:
This was not caused by ethanol fuel.

When sealant is kept constantly wet with fuel because of a seep/leak and in an environment that provides an oxygen source (on the outside of the tank) it can turn the sealant into goo.
Click to expand...

Isn't there oxygen in the fuel tank at and above the fuel level
 
Not saying its the sealant but I will only use PRC-Desoto (P/S890B2 or equiv) inside fuel tanks. Been using it my whole life and never seen a problem.
 
RFSchaller said:
Scott,

Does your conclusion apply to the de-torquing and retorquing of lines at the fittings on the bottom? I recall a thread saying that applying counter torque is difficult and it is possible to develop a leak between the tank and the fitting.

Rich
Click to expand...

No.

There is some risk with just the return line fitting but if proper double wrenching practices are used it is alleviated.

Double wrenching on that fitting is difficult in the limited space under the tank so a modification was done that incorporates the installation of an anti-rotation plate, to prevent rotation of the fitting. It is easy to incorporate the plate to any (removed) tank without opening access to the interior.
 
joedallas said:
Isn't there oxygen in the fuel tank at and above the fuel level
Click to expand...

Not much.
Fuel vapor is heavier than air and for the most part displaces the air from the tank (not 100% but a good portion of it).
If you contact tech support at Flame Master, they will tell you that wetted sealant with constant evaporation of the fuel into air (outside of the tank) will get soft/gooey.
 
Last edited:
rvbuilder2002 said:
Not much.
Fuel vapor is heavier than air and for the most part displaces the air from the tank (not 100% but a good portion of it).
If you contact tech support at Flame Master, they will tell you that wetted sealant with constant evaporation of the fuel into air (outside of the tank) will get soft/gooey.
Click to expand...

Thanks
I leaned something new today

Joe
 
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