Fuel tank leak

[G0165]

I am after some sealing product advice. I have a plastic moulded fuel tank/seat in a gyro which has a leak. The outlet of the tank has an aluminium socket moulded into the bottom of the tank. The fuel is leaking between the plastic and the aluminium. Does anyone have a suggestion on a product and method to repair leak. Obviously the sealant needs to be unaffected by fuel. Thanks

 

[Sv.grainne]

This will work.

Permatex® PermaShield® Fuel Resistant Gasket Dressing & Flange Sealant, 2 OZ – Permatex

www.permatex.com

 

[Mayfield]

Is it a seat tank? Is the aluminum outlet in a grommet pressed into the tank?

Jim

 

[rancherman]

Unless there's some miracle sealant, I'm thinking you may have to eliminate that molded-in-place fitting.. (drill it out) sealing anything on the OUTSIDE of the tank is short term at best.

There are some pretty neat 'blind' bulkhead fittings that can be installed from the outside. Can't say I've seen one for gasoline, only for diesel oil.

But I've installed regular fuel bulkheads in plastic tanks that have had the nipple busted off.
Can't get your hand into the tank to install the fitting from the inside, so I used a piece of wire- through the new hole, and up through the filler neck- then send the hardware down the wire- where it's pulled into place and secured on the outside.
There's many to choose from, and all will have fuel proof gasketing.
google racing fuel cell fittings

 

[Aerofoam]

Second that motion, but you could carefully dissect the aluminum fitting without enlarging the original hole.
I would opt for a fuel proof silicone grommet for simplicity and lack of "Hardware", the fuel tubing, if it is a tight interference fit,
will seal against the grommet, the grommet seals agains the plastic tank and all of it happens with pressure and stays flexible.
Grommets of all sizes and shapes are available at McMaster Carr.
I used some large ones to make mufflers out of SS water bottles, so they could be torn down and cleaned, then loaded on commercial airlines....
The airlines have issues with anything that potentially had fuel in it, so the engine and exhaust needed to be flushed clean....

 

[G0165]

Thanks for the prompt replies. Mayfield it is a seat tank the fitting does not appear to be in a grommet it looks as if it is moulded into the bottom of the seat plastic.

I was wondering wether a wick in loctite product would be worth trying

I tend to agree trying to seal it from the outside with a fillet of sealer is probably going to be short term fix

Woundering if I was to die grind some plastic away from the fitting and take the tank to a plastic welder would it be successful

 

[drthomasd]

I am after some sealing product advice. I have a plastic moulded fuel tank/seat in a gyro which has a leak. The outlet of the tank has an aluminium socket moulded into the bottom of the tank. The fuel is leaking between the plastic and the aluminium. Does anyone have a suggestion on a product and method to repair leak. Obviously the sealant needs to be unaffected by fuel. Thanks

If you are looking for a permanent solution consider 3M DP8005 sealant. Binds to polyethylene and metal. Not cheap and requires a mixing gun but will do the job.

https://www.3m.com/3M/en_US/p/d/b5005321032/

 

[Aerofoam]

Thanks for the prompt replies. Mayfield it is a seat tank the fitting does not appear to be in a grommet it looks as if it is moulded into the bottom of the seat plastic.

I was wondering wether a wick in loctite product would be worth trying

I tend to agree trying to seal it from the outside with a fillet of sealer is probably going to be short term fix

Woundering if I was to die grind some plastic away from the fitting and take the tank to a plastic welder would it be successful

If it has a molded nipple, cut it off, drill it out and go for the grommet, or a compression bulkhead fitting.
It is probably polypropylene and nothing bonds to that anyway....

 

[Chook]

Thanks for the prompt replies. Mayfield it is a seat tank the fitting does not appear to be in a grommet it looks as if it is moulded into the bottom of the seat plastic.

I was wondering wether a wick in loctite product would be worth trying

I tend to agree trying to seal it from the outside with a fillet of sealer is probably going to be short term fix

Woundering if I was to die grind some plastic away from the fitting and take the tank to a plastic welder would it be successful

Hi G0165. I have just recovered my fuel outlet system from a 40L Gerry Goodwin tank where some nitwit had used a tapered fitting into the aluminium tank insert and split it (I am replacing this tank with a 70L one). This outlet unit has been on the tank for 13 years and performed flawlessly with everything from 95 to 98 grade fuel.
These tanks had a very small water collection point which promptly let the water into the fuel system and thus the tap and stainless capture with a push to open valve on the base to be able to separate the water during preflight.
The seal which covered the original ali insert is good old proven cork which was sealed with "aviation gasket Goo". I may have used Permatex high performance thread sealant on the brass to ali threads within the tank.

With these particular tanks, the less messing about with them the better!

Regards.......Chook. G133 & G707