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Fuel Quick drain leak

LettersFromFlyoverCountry

Well Known Member
My Quick drain fuel drain is leaking. I think I've read that there's an O ring in there that usually is the culprit. Anyone know offhand what size that is? Maybe I can find one over at Ace.
 
You can usually just pull them out and clean the debris from around the O ring.
 
More Often, It's Debris In The Tank

Bob:
Before you pull the drain, try "working" it up and down. If that doesn't work, you can pull the fitting, but as already mentioned, you can more likely just clean it. I carry a spare valve assembly, so I can easily swap it out. Both times I've done so, it only required cleaning.
Terry, CFI
RV9A N323TP
 
Always have a spare

I keep a spare with a fresh O ring ---- easy to change them out (not more than 10 gallons of fuel down the arm) (just kidding, only a little spillage) -- I have spare O rings and just "rebuild" the leaker and have it ready to go back the next time.
 
McMaster carries Viton o-rings which work perfectly and are ethanol resistant, for those of you who may use the forbidden fuel. Part number 9464K11 will get you 100 of the little buggers.

Bob, if you need a few send me a quick PM with your address and I'll throw some in the mail.
 
Anyone have a part number for a plug to screw in the sump drain? Might be handy to have on a trip if you find a drain leaking and don't have another drain/o-ring to replace it
 
Anyone have a part number for a plug to screw in the sump drain? Might be handy to have on a trip if you find a drain leaking and don't have another drain/o-ring to replace it

Any 1/8" NPT plug will do. Probably only a couple dollars at your local home improvement store in the aviation plumbing aisle.

If you want to spend a few more dollars for a drop-in replacement to have on standby in the repair kit, Spruce has them here:

http://www.aircraftspruce.com/pages/ap/fuel_drainvalves/saf-airdrainvalves.php

It's part number CAV-110. Vans has them too, same part number.
 
I fought this issue for 5yrs. Then an A&P friend of mine suggested I change the regular brass fuel drain with a Stainless Steel fuel drain. I spent the extra $$$, bought a set of them and Viola, I have not had a fuel drain leak of any kind in the last 3 yrs.

:cool:
 
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What issue were you chasing? If you have some schmutz or an aluminum chip on your fuel drain O-ring causing a leak, how would a stainless version be any better than brass?
 
Long build time drain O-ring deterioration

After 'bumping' the drain several times after checking the sump I finally pulled the drains to clear any filings only to find both trash AND very bad O-rings.

After 7 years of building it never occurred to me that the O-rings would need replacement from just sitting in the parts bin. McMaster Carr Viton O-rings ordered :)
 
After 7 years of building it never occurred to me that the O-rings would need replacement from just sitting in the parts bin. McMaster Carr Viton O-rings ordered :)

Mine too. Phase 1. One started a solid stream of fuel right after a sump check prior to flight. Scrambled to come up with a 1/8" NPT capable plug.

On removal I found a completely dry rotted ring that broke into multiple pieces when I tried to remove it. The other wing was the same way. New O-rings plus spares in the travel kit.
 
My left tank quick drain gave out right after I read this thread. I replaced it with a 1/8" NPT pipe plug. I 'googled' BUNA N and Viton,
http://www.metrogasket.com/o-rings/material_selection_guide.htm the two common materials used in O rings. The BUNA is good to -40F to + 250. the Viton is -20F to + 400. They are both tolerant of ethanol and methanol, however the BUNA isn't so good with Acetone? I use Acetone to clean parts, so I might have killed the original O ring years ago when I built the wings, it just took this long to fall apart.
I got several of both, but I reassembled with the original type BUNA O ring. 1/4" OD, 1/8" ID 1/16" thick. Anyway, I have spares in my flight bag now.
I spilled maybe 2 or 3 tablespoons of gasoline making the change, the tank was more than 1/2 full. Just get everything ready and work fast.
 
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Sump drains

For the proper stainless steel sump drains with the good O-rings check Safe Air CAV110 SS
 
When replacing a drain fitting, I take it that you do not use any kind of sealant on the threads. No tape.

Just use the bare fitting, correct?
 
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Fuel lube

I second that, fuel lube!
Keep a spare drain in your flight tool bag and a few extra prongs, you can get everything from Aircraft Spruce.

While your waiting for parts, find a friend to hold their finger on the open hole while you clean out the trash that is stuck under the oring. Then put it back together to stop the leak.
 
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To greatly reduce the loss of fuel during the removal of the drain valve.....

1. shut off the fuel valve, or switch it to the other tank.
2. Have someone hold their finger over the end of the vent line. If you use tape, REMEMBER it's there....REMEMBER it's there.

If you have a good seal on your fuel cap, your loss of fuel as you remove the drain should be just about "O".
 
To greatly reduce the loss of fuel during the removal of the drain valve.....

1. shut off the fuel valve, or switch it to the other tank.
2. Have someone hold their finger over the end of the vent line. If you use tape, REMEMBER it's there....REMEMBER it's there.

If you have a good seal on your fuel cap, your loss of fuel as you remove the drain should be just about "O".

Did this several years ago with suprisingly minimal fuel loss - just be quick, but not too quick;) Slow is smooth and smooth is fast. Another good tip, and one that is obvious, but I didn't think of, is to wrap a rag around your wrist on the hand removing the valve. Prevents what little fuel that does come out from running down to your armpit:D
 
Recognizing it isn't an option on the road if you have a leaky fuel valve but if I'm at home base, I use it as an opportunity to drain all the fuel out of the tanks into 5-gallon jugs (strained). I figure if there's **** gumming up the valve, there's **** in the tank that needs to come out.

This is particularly an issue, I think, with those of us who polish, especially those who dust with flour after. It gets around the fuel cover and a few grains end up in the tank.
 
so my drain was leaking, I had a spare, and swapped them out. No big deal. I inspected the leaker, and found that there were some small debris sticking to the o-ring which likely was causing the leaking. I was planning to replace the o-ring and keep the unit as a spare since I had two extra o-rings but I can't figure out how to get the old one off... and putting the new ones on looks like it could be a trick too.

Any suggestions? Tips/tricks?
Thanks
 
so my drain was leaking, I had a spare, and swapped them out. No big deal. I inspected the leaker, and found that there were some small debris sticking to the o-ring which likely was causing the leaking. I was planning to replace the o-ring and keep the unit as a spare since I had two extra o-rings but I can't figure out how to get the old one off... and putting the new ones on looks like it could be a trick too.

Any suggestions? Tips/tricks?
Thanks[/QUOTE
I use a dental pick, the type that has a 90deg. bend. Not much concern for the old one, just go at it. On the new one, catch the edge on the flange, hold with your thumb, and then use the pic to stretch it over the other side. Just be careful it to nick the o ring. A bit of heat from a heat gun or hair dryer helps if it is cold.
It's easier than it looks.
 
fuel drain O rings

Harbor Freight Viton O-Ring Kit has many different sizes, and the smallest size just happens to be just right for the fuel drain.

Item #67525
 
Why not use the SA-18 (also known as the F91-18? The flush valves have a lower profile.

-Marc
 
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