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Such A Thing As Lube For the O-Ring Fuel Cap?

Gas Cap Crud: Or Cleaning

Yesterday, finished the yearly inspection. My mechanic was listening when I mentioned found some junk in my left fuel tank.

It wasn't slosh! It was corrosion from my fuel caps; This post is what I found and how I fixed it.

At the start of the thread mentioned the lube for the caps. Well Dale educated me on fuel caps! Learned allot here on VAF, push the pin was a big help! However the reason why you need to push it down is corrosion has set in.

Dale told me that the little o-ring does not stop water from getting into the parts of the cap. Even if just outside in one rain fall you will have nasty stuff building up.

When learning to weld aluminum, the first step is too clean and then re-clean the areas to be welded. Just don't clean too much at a time. Air starts the corrosion process on aluminum as soon as you clean it.

The corrosion layer actually protects the aluminum.

To clean aluminum you will want a Stainless steel brush. Carbon steel creates a different kind of corrosion that isn't good for aluminum.

SS brush and a good Stainless Steel gun cleaning brush too. I used a .40CAL one. It fit perfect for cleaning the inside of the cap pieces where the SS shaft resides.

Safety glasses will keep the mess out of your eyes and the Acetone used to help clean.

The process takes 30-45 minutes per cap for a good thorough cleaning.

Here are some photos showing the breakdown and what you will be cleaning.

Please note, Dale as he was leaving for his normal place of work, mentioned, "Better leave before you break your cap". Thinking about this didn't stop the Neanderthal from doing just that.

Trying to take the cap apart, I used a crescent wrench on the lifting lever so I could get some torque on the nyloc nut on the bottom of the shaft. Yep, small roll-pin that holds the lever to the shaft broke! Nut was stuck solid.

Dale soon returned with a new roll-pin and proceeded to use some channel locks on the outside edge of the bottom part of the cap. Left some teeth marks, used a needle file to tone them down some, the nut finally came free with some LPS1 to loosen things up. Second cap came apart easier once I knew the technique.

Here are some photos with comments:

One cap apart the other waiting to be cleaned:
GC1.jpg


Corrosion under the big o-ring:
GC2.jpg


Parts, notice new roll pin? The glue looking stuff near the top of the cap is the "EZ-Lube" talked about during this thread. Nothing easy about removing it!:
GC3.jpg


YUK! Note crude on threads just from un-screwing the cap, 1998 build up to present, you can see that the bottom part of the cap has threads in it in this photo:
GC4.jpg


A real quick Stainless Steel brushing has this to show!:
GC5.jpg


Stainless Steel shaft. Note corrosion from aluminum on o-ring and shaft, in the top part of cap, see the white stuff where the shaft slides? Now is the time to realize that is why you need to push the shaft down to get the cap to work better when removing it for fill ups:
GC6.jpg


Parts cleaned ready for assembly, several photos showing pile of crud and shiny shaft, along with cleaned parts:
GC7.jpg


GC8.jpg


Stainless Steel toothbrush used to do the brushing, the gun cleaning bore brush (also SS) is in the background:
GC10.jpg


This will now be a yearly project!

Best regards,
Mike Bauer
 
We use krytox almost exclusively in the scuba industry as an o ring lubricant for any kind of oxygen serviced items (which is pretty much everything). Its not Teflon. Its a fluoridated oil with no hydrogen molecule, hence its use in high O2 environs.

For this application - the sliding parts of the mechanism - have at it if you want. But its way way overkill - like using a blunderbuss on a mouse. LPS2 is a more applicable choice in our aviation applications, and esp formulated to not collect dust, protect from corrosion, water intrusion etc.

LPS2 is also compatible with our fuel Orings, and you probably already have it for heim joints etc anyway.

Just my .02.
 
good info

Read the whole thread. Pick your favorite lube... but just USE one.
I had to park outside in a rainstorm in CA and some rain got past the stem and or perimeter seals. It took several flights before it got all the way down to the engine inlet. On climb out, the engine began stumbling. I did an emergency landing and ended up blowing out a brake puck (since the builder put the puck in backwards). The main point is, we all use hangars as much as possible. But, Murphy will do his best to ruin your day on takeoff someday. Be prepared and most of all, have some fun.
 
Yesterday, finished the yearly inspection. My mechanic was listening when I mentioned found some junk in my left fuel tank.

It wasn't slosh! It was corrosion from my fuel caps; This post is what I found and how I fixed it.

At the start of the thread mentioned the lube for the caps. Well Dale educated me on fuel caps! Learned allot here on VAF, push the pin was a big help! However the reason why you need to push it down is corrosion has set in.

Dale told me that the little o-ring does not stop water from getting into the parts of the cap. Even if just outside in one rain fall you will have nasty stuff building up.

When learning to weld aluminum, the first step is too clean and then re-clean the areas to be welded. Just don't clean too much at a time. Air starts the corrosion process on aluminum as soon as you clean it.

The corrosion layer actually protects the aluminum.

To clean aluminum you will want a Stainless steel brush. Carbon steel creates a different kind of corrosion that isn't good for aluminum.

SS brush and a good Stainless Steel gun cleaning brush too. I used a .40CAL one. It fit perfect for cleaning the inside of the cap pieces where the SS shaft resides.

Safety glasses will keep the mess out of your eyes and the Acetone used to help clean.

The process takes 30-45 minutes per cap for a good thorough cleaning.

Here are some photos showing the breakdown and what you will be cleaning.

Please note, Dale as he was leaving for his normal place of work, mentioned, "Better leave before you break your cap". Thinking about this didn't stop the Neanderthal from doing just that.

Trying to take the cap apart, I used a crescent wrench on the lifting lever so I could get some torque on the nyloc nut on the bottom of the shaft. Yep, small roll-pin that holds the lever to the shaft broke! Nut was stuck solid.

Dale soon returned with a new roll-pin and proceeded to use some channel locks on the outside edge of the bottom part of the cap. Left some teeth marks, used a needle file to tone them down some, the nut finally came free with some LPS1 to loosen things up. Second cap came apart easier once I knew the technique.


This will now be a yearly project!

Best regards,
Mike Bauer

Insightful. Thanks!
 
Krytox 8 month Update - thumbs up!!

It has been nearly 8 months since cleaning my caps and applying a super thin film of Krytox .

I am happy to report that the caps still open easily and do not need to be turned to pull them out. The floods at OSH yielded no water intrusion. The tanks have been filled to the lip on several occasions, so have had a good wetting opportunity by 100LL.

No other lube lasted this long (for me).

The test continues. The minimum goal is to last until annual, but I will not touch the caps until the tab force increases or they require turning to release when moving. This is just to see how long it might retain its lubricity. A brutally honest report will result, as always, regardless of the performance.

As always, YMMV
 
ez turn fuel lube

The test (see post 49) is now going into month 9. NO signs of breakdown. Works good and have not had any water from washing or rain since using it.
 
2nd Annual (18 months) - Krytox still slippery

It has been nearly 8 months since cleaning my caps and applying a super thin film of Krytox .

I am happy to report that the caps still open easily and do not need to be turned to pull them out. The floods at OSH yielded no water intrusion. The tanks have been filled to the lip on several occasions, so have had a good wetting opportunity by 100LL.

No other lube lasted this long (for me).

The test continues. The minimum goal is to last until annual, but I will not touch the caps until the tab force increases or they require turning to release when moving. This is just to see how long it might retain its lubricity. A brutally honest report will result, as always, regardless of the performance.

As always, YMMV

OK, so another update. 3/2021 I have not touched the caps until now, my second annual since first using Krytox 205 on my fuel caps. Although they still were still slippery and worked well, the o-ring was removed, lubed with 1MM^3 of Krytox each. Not even a BB size. That .5 cc tube will be a life time supply. Never in the test period did I need to push in the plunger, just opened the lever and pulled up even down to zero F.

Is Krytox overkill? - this experience would say, no, just the correct lubricant for completely trouble free operation of Usher Precision fuel caps.
 
OK, so another update. 3/2021 I have not touched the caps until now, my second annual since first using Krytox 205 on my fuel caps. Although they still were still slippery and worked well, the o-ring was removed, lubed with 1MM^3 of Krytox each. Not even a BB size. That .5 cc tube will be a life time supply. Never in the test period did I need to push in the plunger, just opened the lever and pulled up even down to zero F.

Is Krytox overkill? - this experience would say, no, just the correct lubricant for completely trouble free operation of Usher Precision fuel caps.

+1. Same experience as Bill.

I have been using Krytox on the fuel caps for the past 6 years. I clean and relube the caps every 2nd annual, just because, not because the caps are stiff to open. I fill up after each flight, which means about 100 cap open and closings per year. FWIW.
 
Having tried many of the lubes listed herein the easiest was a drop of 100LL every time the cap came off. Grease, EZlube and others washed off after 4-5 flights and back to dropping fuel. So . . .

I did a little research on the solubility of DC-4, DC-2, EZlube, Lubriplate Lithium, and many others in 100LL. All were soluble in gasoline

I finally found a pure PTFE product called Krytox GPL-205. It claimed not to be soluble in gasoline so I cleaned the caps and o-rings then applied the Krytox. Three BB sized balls and worked it around. A tiny smear on the pivot too.

8-9 flights and three fills to tip top and it the operation is still butter smooth. If this works, a small tube will last till TBO.

BTW - a 0.5 OZ tube was over $20, so not the cheap solution but hopefully it is lasting.

I think I need better bait. It's clear many people don't read past the first sentence. With this lube, the cap does not stick and need the press after lifting the tab.


+1 for Krytox

I rebuilt my fuel caps about 18 months ago and haven't re-lubed them since, and they still work like new.

Like everyone else says it's probably from EZTurn/Fuel Lube. It gets gummy and the big o-ring ID doesn't expand increasing the size of the o-ring when squeezed by cap halves. Instead of the o-ring squeezing out to seal, it just flattens out, which isn't as effective at sealing, so people adjust the cap making hard to insert and remove when loosened.

When properly lubed the o-ring will glide on the nylon of the cap halves and expand with ease...in fact you can do it by hand, very little pressure is required by the cam action of the cap lever.

EDIT: Didn't realize how old the original post was...Krytox is still great
 
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We've also been using the Krytox golden tube for a number of years and often comment about the "early years" without it. The fuel caps just work with it. The guys running the fuel truck don't even need to be told the "push, then pull" trick...
 
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