gas proof silicone

[Norm]

Does anyone know of a general purpose silicone type product that is resistent to gasoline?

[dlearl476]

Will this work, Norm?

Permatex Ultra Black silicone gasket maker or dressing cures fast. Apply a bead of Ultra Black in room temperature to create reliable, sensor safe, low odor, non corrosive gaskets for any mechanical assembly.
This product moisture cures to a tough, flexible rubber gasket that vulcanizes as final torque is applied. It resists oil, aging, weathering and thermal cycling without hardening, shrinking or cracking.

Product Benefits
Typical Applications
Improved oil resistance    Oil pans
Sensor safe, non-corrosive    Transmission pans
Good adhesion and flexibility    Valve covers
Replaces most cut gaskets    Valves and guides
Can be used as a gasket maker or dressing    Timing gear covers
Non-flammable, Non-toxic    Differential covers
Low odor
Meets performance specs of OE silicone gaskets and complies with OEM standards and extended warranty requirements.
PTX-82180 comes in a 3.35 oz. tube.

Or are you looking for a lubricant type silicone?

[Norm]

I've got a drawer full of the usual ones, but they tell me that none of them will hold up to gas. I've heard the ultra blue is a "little bit" resistent, but that doesn't sound very comforting.
I want to add a little silicone to an outer gas cap ring (the one with the green "O" ring), that seems to weep a little when lofted, but I want to make sure I don't need a crowbar to get everything off some day. I also don't want to disolve silicone into the gas tank.
Surely someone has dealt with this before??

[Langanobob]

Norm,

For stuff like that I've been using a very light coat of Yamabond also known as Hondabond, Threebond and maybe even packaged as Duckbond?

In spite of the "bond" in the name it still comes apart fairly easily and I use just enough to cover the o-ring or mating surface. 

I got disillusioned with Silicone sealants a long time ago.  Maybe they've improved but they had a tendency to squeeze out into long thready strings that come loose inside a motor and get everywhere.   Too hard to get the exact amount to cover the mating surfaces and not squeeze out on the inside.

[MotoCreations]

I have a baby jar of stuff called "aircraft lube" or sometimes "fuelers lube" -- it gets applied on all the rubber seals and waterproofs things with fuel fittings / o-rings / etc.  Doesn't dissolve at all!  No clue what the real name is.  Friend was an aircraft mechanic (Boeing assembly) and swore by the stuff to prevent minor leaks -- he gave me a large dollup in a jar and said it should last a lifetime.  It's like a super sticky version of Vaseline. (no bad jokes please!)  Ask around your aircraft supply shop.  They have some unique silicon-based items there that one normally wouldn't expect.

[michalik.piotr6837]

Just buy the new O-ring, ya, they're expansive but unless you want gas on your tank when you lift it, they're worth it.

[Ivan]

Look for Anaerobic Gasket Maker.  Permatex is one source, Napa autoparts usually has it or they can at least get it.  It comes in a blue tube, mine is Permatex P/N 51813.  It aint cheap.

The o-rings are notorious for not sealing well on the bottom of the plastic Aprilia fuel tanks, because the bottom of the tanks tend to warp.  The anaerobic gasket maker is the only reliable way to get a good seal, and is recommended by the factory.

[Kurt V]

You need DOW RTV730 solvent resistant sealant. Not cheap. Will run you about $80.00 a tube, but works. Used in the aircraft industry.

http://www.skygeek.com/rtv730-3oz.html

[dlearl476]

I want to add a little silicone to an outer gas cap ring (the one with the green "O" ring), that seems to weep a little when lofted, but I want to make sure I don't need a crowbar to get everything off some day.

AFAIK, the permatek black would do what you want it to, but I'd check the O ring and mating surface first.  I've never had a problem with mine and I just use plumbers lube (silicone goo) to lube the Oring.  If it's perfect and the mating surface flat, it won't leak.

[Langanobob]

Norm,

Not sure you're getting enough opinions, so thought I'd add another one. 

Silicone sealer doesn't actually dissolve in gas, say the way sugar dissolves in hot coffee.  Gas will kind of weaken it and make it sort of crumbly.  But in your case, if you put a very thin coat of silicone on the surface, barely enough to make it wet the gas will only see the extremely thin edge of the sealer, if that.  If any should squeeze out it will not dissolve, and will not get past the fuel filter.   But if you put it on very thin, none will squeeze out.  If you can't find the stuff Motocreations and others have suggested, I'm sure that a very thin layer of basic old silicone gasket sealer will work fine.

[woppini]

RTV/silicon will not work with your o-ring. It also wont work with fuel, nuff said. If you want to seal the part, get a new oring, or get some permatex aviation seal. Its a thick liquid you can by in a tube, or small container with a brush. Usually any good autoparts store will carry it. Not pricey by any means. Its fuel proof, and doesnt fully cure hard. This will allow the oring to contract and expand with movement like it was designed to do.

[Norm]

Thanks guys, exactly what I'm looking for. I'll get some of all of it, lot's of room in my gook drawer.

[Langanobob]

Thanks guys, exactly what I'm looking for. I'll get some of all of it, lot's of room in my gook drawer.

Norm, we tried!  Maybe try TOB, you'll probably only get one answer there