Replacing wing tank quick drain

Steve Brown · #1 05-25-2008, 08:55 AM

Yesterday for the second time I replaced the quick drain on the copilot side wing tank.

The first time the rubber seal was completely missing and the thing was leaking at an alarming rate. This time it wasn't leaking as bad, but way too much to leave it.

When I got it off this time, I was surprised that the seal (O-ring) was intact, but an aluminum shaving was deforming it, allowing a leak. I had tried to clear any such problem by draining a lot of fuel through the valve, but apparently this chip was too large to get through.

Last time I drained the tank completely before replacing the valve. This time I decided to take one builders advice and just do it quickly before loosing too much fuel.

Takes two people.

I prepared the new one with fuel lube in advance and had my wife holding that one. When I removed the old one, I plugged the hole with my thumb until I was ready to put the new one in. It worked fine. I lost some fuel into a towel, probably less than a liter.

I'm thinking I have chips in the tank left over from construction. The first time I did this dry, which didn't allow those chips to get washed out. I'm hoping that the fuel I lost in this process was carrying the rest of the chips with it.

By the way, in case anyone is as dense as I am, replacing the O-ring does not require removing the retainer ring (or whatever its called) on the valve. I removed it on the first one I fixed before realizing that. Then it was obvious that the O-ring will easily push over.

John_RV4 · #2 05-28-2008, 12:02 PM

Anybody had a fuel drain they couldn't remove ? I did the left tank this week and the old one came out easily. I then tried the right tank and I started to strip the nut on the body of the drain. It is stuck tight.

I was hoping somebody might have a clever solution before I get out the big breaker bar :-).

John

mannanj · #3 05-28-2008, 09:04 PM

Nothing cleaver on removing.

On installing pipe thread joints, ALWAYS use something like "fuel lube" (I think that's the name of it) or any of the aluminum anti-seize compounds. You can get them from Aircraft Spruce or one of the other suppliers to make sure that the threads don't gall if you ever have to remove them.

If the threads gall on removal, you will probably have to chase the threads with a pipe thread tap on the threads on the tank that were galled when you removed the quick drain. This should not be a big deal, but will seat the quick drain a little deeper into the tank "bung". Remember to flush out all the aluminum shavings.

Hope this helps. If you have questions, PM me with your phone # and I'll try to explain further.

Dave Dollarhide · #4 06-01-2008, 09:04 AM

I periodically pull my tank train valves to flush the tank, as many sediments will not pass through the valve when it's depressed. I don't drain the tank, but simply plug the tank vent, place a fuel container below the valve, with a screened funnel in the top.

With rubber gloves on and a spare valve handy, I remove the valve and let it flow. In short order, a vacuum develops in the tank and the flow is reduced to a few drips. Before it "gasps for air," I screw in the spare plug, with little fuel loss.

I inspect and clean any debris from the valve's o-ring, then check the screen in the funnel to see what is there. Maybe I should, but I don't use any lubricant/thread sealer, as a dry fit always seals properly. The product to use is EZ Turn, which I use to lubricate my tank transfer valve, but it's a great sealer also. http://www.aircraftspruce.com/catalo...ezturnlube.php

bpattonsoa · #5 06-01-2008, 07:18 PM

I had a puddle under my right tank last week, just when fuel went over $5/gallon.

The "O" ring was shot, so I replaced both tanks to prevent it happening next week on the other tank. I did use fuel lube when they were installed 5 years ago. Both came out easily. Suspect that residual is enough to keep them from sticking next time.

......... This thread gave me an idea for fly ins, when it gets slow. We can have a drain valve swap out race. Winner is the one who can do it with the least fuel loss. The winner, if properly publicized, could make minor money, especially with current and future fuel prices.

Bruce Patton

Kyle Boatright · #6 06-01-2008, 08:17 PM

Quote:

Originally Posted by bpattonsoa

I had a puddle under my right tank last week, just when fuel went over $5/gallon.

The "O" ring was shot, so I replaced both tanks to prevent it happening next week on the other tank. I did use fuel lube when they were installed 5 years ago. Both came out easily. Suspect that residual is enough to keep them from sticking next time.

......... This thread gave me an idea for fly ins, when it gets slow. We can have a drain valve swap out race. Winner is the one who can do it with the least fuel loss. The winner, if properly publicized, could make minor money, especially with current and future fuel prices.

Bruce Patton

I've replaced the drain in a nearly full tank and only spilled as much fuel as I'd typically get in the fuel sample test tube.

I was impressed with myself. Which means that the next time I try it, I'll dump 19 gallons of low lead in the hangar by accident...

John_RV4 · #7 06-02-2008, 07:42 AM

Yeah, I got a little cocky and tried to do the right tank quickly. That's how I stripped the nut. I hereby withdraw from the contest, since I've got one I can't get out (yet). I reserve the right to re-enter once I get the new one installed :-)

John

49clipper · #8 06-08-2008, 09:51 AM

I could not drain mine at all. They would not push up. I loosen ed them about three turns and they work fine. When tightened up they do not work. They must be apparently hitting the fuel pickup tube. Both sides. Anyone have this problem. I can't leave them loose obviously. What if I pull them out and with a small punch, try and bend the pickup tube up slightly? About a 1/4" should do it.

PeterB · #9 06-23-2008, 01:12 AM

Had a road side repair done once where the bottom connector to a diesel fuel tank got sheared off. I stopped it with a quick temporary repair when the company mechanic showed up. He had seen this before so he was ready. The first thing he did was replace the fuel cap with another that had a simple T-brass fitting on top. Connected it to an air compressor and ran air through the top of the T. This caused a vacuum that stopped the leak entirely. Same principle as your paint sprayer, just no tube down into the fuel. In the case of aircraft you would have to plug the air vent. He was then able to fix the broken connector at his own pace.
Peter
unknown mechanic.

Norman CYYJ · #10 06-23-2008, 06:52 PM

I have experienced this on several aircraft. Each time it was either tank sealant or sealant that was placed on the drain plug. Take the plug out and run an exacto knife around in there. That should clear up your problem. Make sure the **** comes out of the tank and doesn't stay behind to give you grief down the road.