Leaking fuel cap question

LarryT · #1 08-05-2010, 08:03 PM

My trip to Oshkosh was the first time N544WB was outside overnight when it rained.

No water in the left tank, but water in the right tank when sumped. I assume that is indicative of a leaking fuel cap on the right side. Because this cap leaks fuel when lineman ignore my request to leave some expansion volume in the tank, I also presume that the cap is leaking around the stem.

The aircraft was completed in 1997 and has the black o-ring. Looking at the Van's catalog, it appears that this cap has been superceded by a cap that uses a brown o-ring, that service parts are not available for the older cap and that the older and newer style caps are not interchangeable. Am I correct that I need to replace the entire cap with the newer model?

Confirmation of the above from knowledgeable individuals is welcome. Thanks in advance,

LarryT

Geico266 · #2 08-05-2010, 08:07 PM

The same thing that happened to you has happened to me a couple of times. Now, if the plane is going to sit outside for any length of time I try and cover the caps to prevent water entry. Blue masking tape works good.

Just replace the o-rings, no need to replace the cap, IMHO. Study the left one to see that the right one is assembled correctly, but I would replace all of the o-rings at this point in time. They can be made to be water tight but why take the chance?

Ron Lee · #3 08-05-2010, 08:43 PM

I cover mine with painters tape.

turbo · #4 08-05-2010, 08:48 PM

they are designed not to leak if adjusted properly.

there you go, i fixed that.

RV6_flyer · #5 08-05-2010, 08:55 PM

Quote:

Originally Posted by LarryT

My trip to Oshkosh was the first time N544WB was outside overnight when it rained.

No water in the left tank, but water in the right tank when sumped. I assume that is indicative of a leaking fuel cap on the right side. Because this cap leaks fuel when lineman ignore my request to leave some expansion volume in the tank, I also presume that the cap is leaking around the stem.

The aircraft was completed in 1997 and has the black o-ring. Looking at the Van's catalog, it appears that this cap has been superceded by a cap that uses a brown o-ring, that service parts are not available for the older cap and that the older and newer style caps are not interchangeable. Am I correct that I need to replace the entire cap with the newer model?

Confirmation of the above from knowledgeable individuals is welcome. Thanks in advance,

LarryT

The newer (Brown O-Ring) is a replacement for the OLD Black O-Ring cap. Both caps need "Fuel Lube" applied to all moving parts. The OLD BLACK O-Ring cap was discontinued over 14-years ago. It is time to replace yours.

I had the OLD cap supplied with my kit but never flew with it. I have always flown with the NEW cap. It DOES NOT LEAK after applying fuel lube to all parts including the the center stem and small o-ring.

There are over 2,410 hobbs hours on my RV-6. It will be 13-years old in September.

zilik · #6 08-05-2010, 09:01 PM

Quote:

Originally Posted by turbo

they are designed to leak if adjusted properly.

Interesting. Why would you say they are designed to leak if adjusted properly? Each year I pull my caps apart for a good cleaning. I use fuel lube on the o-rings and adjust the cap so they open and close like I like them to. I say how I like them because some people like loose caps and some like tight. I have never had a leaky cap, fuel or water. The plane has set out in torrential downpours and long soaking rains and I have never found water when sumped. My caps are circa 1996 and have the brown o-rings.

Lycosaurus · #7 08-05-2010, 09:20 PM

Quote:

Originally Posted by zilik

Interesting. Why would you say they are designed to leak if adjusted properly?.....

Turbo said:

i don't think........
they are designed to leak if adjusted properly.

Mike D · #8 08-05-2010, 10:08 PM

I just had the same issue.
What I found was that the two big aluminum parts started to rust in-between. I was told this was because of the interaction between the stainless steel and the aluminum, but I am not a metal expert. This was bad. It started to make the aluminum swell and push the two halves apart. The large O-ring was okay, but the small O-ring was starting to crack and let fuel out and water in.

The solution was a complete cleaning and rebuild. I used fuel lube on the O-rings and adjusted the cap for a proper fit. The last step was to put on the nut to lock my adjustments in.

No more leaks, and they open and close much smoother.

The caps are not too expensive, so maybe ordering the new style would be good. According to the NTSB, water in your fuel is bad.

zilik · #9 08-06-2010, 05:32 AM

Quote:

Originally Posted by Lycosaurus

Turbo said:

i don't think........
they are designed to leak if adjusted properly.

I never seem to catch the title continued into the post. Once I'm in the thread I seldom read the titles. Thank you for the clarification.

AlexPeterson · #10 08-06-2010, 06:40 AM

Don't use Fuel Lube (EZ Turn) if you plan to get them off below about 10 or 20 degrees F. Much has been posted on this, but it comes up every year or so. EZ Turn becomes like tree sap when cold. Miserable stuff to completely remove from fuel caps also. It really, really is no fun trying to get those dang caps off while you are standing in a cold wind, trying to get some movement back in your hands.

I spray mine with TriFlow a couple times a year, and it makes operation much smoother. The o-rings will seal better with less lever force, since you are not fighting friction so much.