The International Cessna^® 170 Association

I continue to have a bit of a fuel leak at both filler necks. With new fuel caps I don't think the caps are the problem. I am curious about how the filler neck (p# 0523529 [-1 for early 172's]) is secured to the fuel tank adapter (p# 0311240). Drawings in both the C-170B & C-172 Illustrated parts catalogue would indicate that it is screwed into the adapter (moat). If so how is it secured to prevent its unscrewing when fuel caps are opened/closed? Its been too long since I replaced the gasket under the adapter for me to recall how it is secured.

Frank, hope these pictures help and also apply to your 170C.
This photo shows how to drop the filler neck down into the tank to remove and replace the inner gasket
This shows the two new gaskets ready to install. One inside the tank and the second outside the tank, but beneath upper tank flange (unpainted on red rag). Slide the inner gasket down the wire holding the filler neck. Pull the filler neck and gasket up carefully. Align all the parts and gaskets. Place the outer gasket around the filler neck. Place the tank flange over the gasket (again making sure the parts are aligned). Then install the screws holding everything together with the tank.

If you need more pictures, send me your email via PM

Wow Jim.....nice pictorial.....I'm sure a lot of people will get a lot of mileage out of what you sent....thanks!!!

Thanks Jim! Good, clear photo's. I didn't know these gaskets could be changed without pulling the fuel tank cover/panel. This method would save a lot of labor/time. At this point I am not sure if these two gaskets are what need to be changed or not. I changed one many yrs ago & had to remove the wing panel. Sure had fun getting some of the old screws out.

In my case Frank the filler neck threads are staked (punch) into the adapter in two places. I wish whomever had did that in the past was a thorough as they were. I've wanted to change mine but the thought of beating the heck out the filler neck and then trying to clean up the threads through the fuel tank hole has made me wait until it's a requirement, not just to make it look pretty.

Perhaps you meant you wished they were NOT as thorough, Jim?

Every filler neck I've seen was "staked". Jim's is the only good way to re-align the caps unless one is willing to risk stripping the threads by unscrewing the neck despite the staking job. In any case, Pro-Seal is good insurance against leaking at the threads, and Permatex No. 2 is what I always use on fuel tank gaskets to insure against leaks. (In full disclosure, I've never done a 170 tank.... but I've done other models that were similar.)

That's what I wanted to write Thks.

And,for gosh sake, be sure you get the filler neck oriented so that the cap is in the right place when it is locked down. It is really discouraging to get the job all finished and then find that the ears on the cap are 45 degrees to the slipstream when closed down.

170C wrote:Thanks Jim! Good, clear photo's. I didn't know these gaskets could be changed without pulling the fuel tank cover/panel.

You must remove the fuel tank cover to dot this. The green you see in Jim's photos is the top of the fuel tank not the tank cover.

Thanks to all on this subject. Yea, ole Frank thought he had seen a short cut to replacing the gaskets, but Jim called yesterday and said that that would be too easy and I needed a challenge so I would have to remove the wing panel Having done it once, I suppose I can do it again Jim did point out that the parts catalogue and illustration shows only two (2) cork gaskets (that's what both my C-170B & my C-172 parts catalogue show), but there is a third one needed. Sounds like a project for some day or two when flying isn't on the agenda. I believe Jim said his filler neck was welded into the adapter, but I may have not remembered correctly. Once one has gone to the effort to remove the cover panel one might as well check out the tank, as Jim did, to see what else may be amiss after 52 yrs. One thing about old airplanes, you never have to worry about having something to do to them. There is either something broken, worn out or something we would like to change or modify. Guess that keeps us from getting bored

170C wrote:... There is either something broken, worn out or something we would like to change or modify. Guess that keeps us from getting bored

Airplanes are like women: They always fill the time allocated to them. (And sometimes they requisition additional.)

gahorn wrote:

170C wrote:... There is either something broken, worn out or something we would like to change or modify. Guess that keeps us from getting bored

Airplanes are like women: They always fill the time allocated to them. (And sometimes they requisition additional.)

George......if I'm not mistaking........didn't you post a list of discrepancies between aircraft and women?.....leading us to think there were no similarities?

I believe you might be referring to a posting in which airplanes were considered to have some attributes preferable to women. I did not originate that, but I'm familiar with it. (They can change their minds also. And do.)

Frank, I just did the gaskets on my 170 and that stopped the leaking. As the guys have stated, there are 3 gaskets and not 2 as shown in the parts manual. Not a tough job, just time consuming as it had been a while since my tank covers were pulled. Replaced all the screws with stainless.

Wish I had Jim's pictures before hand, though.

Good luck.

Goods gosh,Kyle. Do you realize that you've just given the "Purists" an opening to fill up about six pages on this forum. Stainless steel screws in the fuel tank cover are not according to the parts specs!