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Fuel Drain Leak

wyoflyer

wyoflyer

Active Member
Before flying the other day, I did my usual preflight and drained fuel from the quick drains on each tank. No water so I hopped in and started to taxi. As I passed the local FBO a lineman kept giving me a stop sign. Stopped, got out and he showed me where my quick drain was leaking. Not just a slow drip, but more like a dripdripdripdrip. Would not have taken very long to empty the tank! Drained the leaking tank and found a badly cracked O-ring. Interestingly, the other one was fine. The cracked o-ring was on the tank that I fill with both av and auto fuel. The other is excluseively av gas.
Just make sure when sumping your tanks that they "really" seal.
 
wyoflyer said:
Before flying the other day, I did my usual preflight and drained fuel from the quick drains on each tank. No water so I hopped in and started to taxi. As I passed the local FBO a lineman kept giving me a stop sign. Stopped, got out and he showed me where my quick drain was leaking. Not just a slow drip, but more like a dripdripdripdrip. Would not have taken very long to empty the tank! Drained the leaking tank and found a badly cracked O-ring. Interestingly, the other one was fine. The cracked o-ring was on the tank that I fill with both av and auto fuel. The other is excluseively av gas.
Just make sure when sumping your tanks that they "really" seal.
Click to expand...

Good catch. This is not an isolated incident and the o-rings can decay over time even in avgas. It's not a bad idea to carry either a spare drain valve or just a 1/8" NPT pipe plug in case an o-ring lets go when you are away from home. The valve can be swapped out without losing hardly any fuel.....just be quick while you use one hand to plug the hole and the other to handle the valve. :)
 
I wonder if any oxygenation additives were in the MoGas at any time and, if so, whether they contributed to the deterioration of the o-ring? Both MTBE and Alcohol can affect certain kinds of seals.

Something to consider...
 
Had the same problem with mine. I just replaced the O ring. Sometimes fine grit will naturally work its way to this spot and when you check for water the grit will inbed under the washer, creating a leak. They o rings are small and cheap.

Chris
RV6A, N613LE
El Paso, TX
 
I'd like to have a few spare in case one gets damaged by debris - I've had mine stick a couple of times with a tiny piece of grit/al in the drain holes. Anyone tell me the sizes of the o-ring, and as I use autofuel it'll have to be viton as well.

Allan
 
I had a quick drain leak only in flight. I could tell by the fuel stains on the bottom of the wing. It was a little debris caught on the 0-ring. Having a spare I just switched it out with loosing too much fuel on the ground.
 
another o-ring to keep in stock

is the quick drain o-ring for the oil sump. These get overlooked on a continual basis. We recommend changing either the o-ring or the quick drain every annual.

Allen
BPE, Inc.
 
Repalce o-ring before install

So I guess, those building and plan to use mogas, best replace the o-rings to start with?! (with viton O-rings)

Regrads, PilotTonny
 
Anyone want to post the specific size of the O-ring for the fuel drain, and maybe even the various oil sump quick drains?
 
2nd that

I second the above post... Can someone tell us the part number for new o-ring. Standard and auto fuel safe?

thanks,

Jason
 
$10 or $0.18

Aircraft Spruce Sells the drain valve and the o-ring. I ordered a spare valve and some spare o-rings. I tried to look them up on their site but the pdf file that they are on is corrupt and will not display. Type in the Vans part# CAV-110 and it brings up the link to the bad pdf. In the 2006-2007 catalog they are on page 163. The part number for the o-ring is MS29513-006 $0.18. I had to replace mine as soon as I started filling the tanks after the years of building.

Your welcome :)
 
More on leaking fuel tank drain o-rings

bhester said:
Aircraft Spruce... The part number for the o-ring is MS29513-006 $0.18. I had to replace mine as soon as I started filling the tanks after the years of building.
Click to expand...

In 4 short months, both o-rings in Vans fuel tank drains are leaking. I use AVGAS exclusively. I solved the problem temporarily with Harbor Freight nitrile o-rings until my Spruce care package arrives. According to the description in Spruce catalog, the MS29513 o-ring

These MS29513 series O-rings are resistant to fuel and are ideal for applications such as fuel injection connections and primers. A small amount of fuel proof grease applied to these O-rings helps the installation and operation of primers. Not resistant to automotive fuels.

They're resistant to fuel but not auto fuel. I assume that means they are not resistant to the MTBE or alcohol in auto fuel. Assuming you use auto gas but avoid auto gas with mtbe and alcohol, are these the right o-rings?

Barry
Tucson - flying 9A, 46 hours and loving it


 
Avgas also

Always use AvGas

I replaced a very leaky drain on the co-pilot side last summer. It was definitely dripdripdripdrip..... Still, I let it set over night then flew it home (2hrs). It lost surprisingly little fuel. I deliberately flew the tank nearly empty. on the way home. Over the next 2 weeks the leaking took care of the rest of the fuel so I got to work on an empty tank.

Same side is now leaking again. The other side has minor seeping occasionally.

I have spare valve and O-rings, so I'll do the work soon.

I'm thinking there are metal shavings or something in that right tank which is destroying the O-ring.


Any other thoughts on why the same side would go bad again????
 
Leaking O ring

I had these fail on my last airplane with the same drains..It usually starts with a slow drip.

I simply went to my local autopats store and bought O rings that were black so I assume they were not Viton (normally brown).

I used autofuel exclusively (and do so today). The replacement rings seemed to work OK.

Now of course Oregon has Ethanol on the way so all bets are off after that.

Guess I'll need to look for a source of viton O rings

Frank

Rv7a IO360 260 hours
 
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