What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

T-406A Gas Cap O-Ring replace

One of my tanks is taking on water from the outside and it seems like the gas cap is at fault. I had an extra gas cap and decided to try to tighten the bottom nut but broke off the roll pin while trying to do that. I ordered 3 sets of replacement parts to overhaul all 3 of my gas caps but I’m concerned that I’ll just break another roll pin when I go to tighten the lock nut on the bottom once I install the new seals. Any pro tips from the crowd?
 
Usher Fuel Caps:

Adjustment instructions and parts shown below. Instead of fuel lube/EZ Turn for lubrication many folks use Krytox GPL 205 grease with good results. Expensive, but the small 0.5 ounce tube will last a long time.

i-CZCx5NV-L.jpg


Parts are available from Van's:

 
Last edited:
Thank you! I’ve got the parts on order just curious if anyone else had trouble getting the jam nut tight without breaking it damaging the lever and roll pin that holds the lever to the threaded post
 
Thank you! I’ve got the parts on order just curious if anyone else had trouble getting the jam nut tight without breaking it damaging the lever and roll pin that holds the lever to the threaded post

Have done several without damaging anything. Grab the base on the initial nut loosening (breaking the initial torque from the base) to keep that force off the pin.
 
I use a vise

I snugup the 83A washer casting in aluminum protected vice to loosen the nut. Once it’s all reassembled and adjusted I put it back in the vise to tighten the nut.
 
The nut doesn't need to be very tight. It just needs to be snug enough to keep the threaded washer casting from loosening. I just hold the washer casting firmly in my hand while I snug up the nut.
 
Roll pin

Also
The roll pin can be replaced if all the other parts are present
It is a basic hardened roll pin, 1/16th in by 3/4 in
Available at most parts stores or hardware stores
 
When I had a roll pin break on one of mine, I replaced it with a drill bit shank cut to the right length because I didn’t have the correct roll pin handy. I don’t remember the number size, but it fit snugly and never broke. The right size roll pin should work if the tension is set correctly.
 
Thank you! I’ve got the parts on order just curious if anyone else had trouble getting the jam nut tight without breaking it damaging the lever and roll pin that holds the lever to the threaded post

Using a little lube on the threads won't hurt, there will still be some drag on reassembly. If it is tight, enough to be concerned for the pin, then something else is wrong.

Krytox is highly recommended, I did an 18 month test with a tiny bit on the o-rings and it still operated easily and smoothly, and sealed too. If it is smooth then it can be properly adjusted to seal and stay that way.

Why Krytox? - -Because it does not dissolve in 100LL - -I could not find any other lubricant that has this important characteristic and has stable properties - i.e. does not get sticky.
 
I purchased 2 fuel caps years ago to have if I needed them. They were the newer style that the back disc was threaded and had a nylon taper. I removed them from the box today to find the fuel lube that was applied during mfg was now a sticky mess and did not allow the cap to work properly.

My old caps that are currently in use needed a new shaft O ring. I have never had them apart and they were stuck. The old model used aluminum for the shaft and had reacted to the nut. I gave it a shot of Aero kroil and used a small impact to remove the nut. By holding the cap in my hand with the lever in the down position, I reduce the risk of breaking the pin.

The small O ring on the shaft is the one that will wear out. And it will allow water to enter the tank. It is also part of the reason the cap does not release when the tab is lifted. It also needs to be lubed with Krytox. EZ turn/fuel lube will gum it up and the cap will need to be pushed on to remove it from the tank. It can't be washed off, it needs to be removed by wiping it off with a rag and a lot of pressure.

Having dealt with both the old and new style, I will say, I like the old style better than the current style. The old style disc was not threaded and not tapered. It floated on the shaft and was held in place with the nut. It pushed the O ring against the taper of the cap and the O ring slid up the taper to expand. To adjust, all you need to do is tighten the nut with the lever closed and then try to press it into the tank with your thumbs only. If it won't pop in, loosen it up a bit. When it does go in, take a pen or something that will fit in the cap recess and try to rotate the cap. It should rotate just a little with a good effort.

The new style is the same except you adjust the threaded disc and when you are content with the fit, you bring the nut down to just touch the disc and keep it's position. The Nylock part of the nut is what keeps the nut on the shaft.

If you ever have to pry up hard to flip up the lever, it is time for cleaning and lube. If you ever need to press hard to latch cap, it's time for cleaning and lube. Under normal use, you should never break a pin. Doing so means something is not working properly.

I am not running auto fuel so the O rings were purchased at NAPA Auto parts
at a cost of .80 cents each for the small 727-2012. And $1.10 each for the big 727-2325 O rings.

The impact I used.... I don't' expect to need it next time. But if I do....
impact.JPG

The lube highly recommended here on VAF...

kry.JPG
 
Back
Top