The International Cessna 170 Association

No, he’s our Hero here and probably else where.

Poncho73 wrote:

Fuel Cap 2.jpg

here we go, I installed an oring between the lower cap surface and washer. fuel lube helps as well.

Thanks, Poncho.

We installed new gaskets and replaced the O-rings on the top side of the caps. The O-ring on the right cap was almost gone and my left cap didn’t even have an O-ring installed. Conducted a test flight today and still leaking on the right side! Noticed that the right cap has a very slight movement where it may not be sealing completely. I will try swapping caps and the extra O-ring on the bottom as your picture shows. Still plugging away at it!

P.S. I am running with fuel selector on both. I’ve thought about running on either left or right to test how that acts as well. I am curious but I am guessing I wouldn’t see as much leaking running on one or the other because it wouldn’t be able to pull from the left tank. Just a thought!

I never had an o ring on the top or bottom. I cleaned the existing parts and only installed a lower o ring where you see in the picture.

Finally got it! Turns out the new gaskets were too thin and were not making a good seal. After getting some gaskets made that were the correct thickness and installing the o-rings as stated in my previous post, it appears the leaks have been stopped. No more blue on the top of my wing and both fuel gauges suggest a much more even fuel burn between left and right tanks. Glad to have this little monkey off my back! And now its time for my annual...

On the 48 fuel cap, they have an oring/ dynaseal under the top washer at the handle. If installed under cap when tightened it will separate the seal and allow air to migrate.

John

Rereading my post I should say that I did not install an o-ring on the underside of the cap. Everything is installed as per original design (see attached image); with new gaskets and a fresh o-ring with some fuel lube. My best guess is that the cause was due to the o-rings deteriorating and that the main gaskets had gotten hard and were not sealing properly between the cap and tank when compressed.

n3833v wrote:On the 48 fuel cap, they have an oring/ dynaseal under the top washer at the handle. If installed under cap when tightened it will separate the seal and allow air to migrate.

John

Believe it or not that was my thought too. Initially I did installed under the dynaseal and no luck. Still leaked. So I disassembled everything, cleaned it, lubed and moved the seal to the lower side. And fixed! No leak, no fuel balance issue. That was about 600 hours ago. Still running good. Cheers