MTFCA Forum

Hi, my sediment bulb outlet petcock seeps gas when the sediment bulb valve is turned on. I wrapped the threads for the petcock with teflon tape but it still seeps. What might be the cause and how can I fix it?

If the small thumb handle on the pet clock turns easy, could be worn taper cylinder valve that cuts off the gas. Or the spring on the backside of the handle is broken. You could try to ‘bump’ the thumb handle back into the petcock to ‘seat’ the valve tightly.

All else you can repair or replace. Typical to close and open even new ones is to slightly bump the rear of the thumb handle to shock it open, or slightly bump (small hammer or tool handle) the thumb end to seat the valve snuggly closed.

EZ Turn Aircraft fuel valve lube is the stuff - It worked great for me .. here's a post from another group:

RE: fuel line thread sealant?
NONE of the readily available sealants are appropriate. This was covered a couple of weeks ago. Fittings in fuel systems should be lubricated/sealed with United Ez Turn Lubricant (aka fuelube), which complies with Military Standard MIL-G6032D. You can buy it at Aircraft Spruce, www.aircraftspruce.com. PN 09-00306 is a 5 OZ tube, $11.70. it's widely used in aviation, where properly installed fuel systems are even more critical than on a boat. (or a Model T )

http://www.mtfca.com/discus/messages/17 ... 1307392255

I am not clear where is it leaking from, the thread where it fits into the tank or the shut off handle? If you used white teflon tape, that is wrong type for gas applications.

Like Mark said, if you're talking about the threads where the petcock threads into the bulb, Teflon tape won't work.
Get a tube of Loctite #567 and your problems will be solved. Works great on gas and oil.

The petcock on the sediment bulb is at the lowest point. The leak may well be higher up. Fuel leaking at the tank outlet will drain down to the petcock. Likewise, leaks at the shut-of valve will also drain down to the petcock. These areas need to be checked first before blaming the petcock. Often, the only evidence from a slow leak will be a stain made by the colourant in the fuel accumulating as the fuel evaporates.

Allan from down under.

I'm with Allen on this - after I do tank work & install the sediment bulb, I put enough gas in to immerse the inlet of the bulb and check for leaks PRIOR to installing the drain petcock - I use a pipe plug for leak testing then verify "all is well" then install a reconditioned or new petcock - works for me !

I took the petcock apart and slathered it with fuel-proof lube -- one tube lasts a lifetime! -- and it seems to be dry now. no leaks that I can tell!

My carburetor connection was leaking too so I used the fuel proof grease on those connections. Dry carburetor now!