Fuel drain sump misaligned?

[akclimber]

And here’s the starboard side.

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Any idea why the strap would break?
And where can one source the fuel tank straps and the filler neck gaskets?

[Bruce Fenstermacher]

Well darn looks like a few worms escaped when you lifted that top.

You can look up the part numbers and order the gaskets or if you can source suitable gasket material, cut your own with templates we have here on the forum. You might end up repairing the strap you have if you can't source one.

Check here for the templates: viewtopic.php?t=12829

BTW you figured out how to attach photos but you can also place the photos in your text rather than let them all be placed at the bottom by placing your curser in the text were you want them to appear then clicking the place in line button in the list of photos. I'll move this photo into your text so you can see the result.

[cessnut]

Pretty easy to fab the straps and gaskets. With the tank removed you can slide a bar up between the fuselage and root rib to buck the rivets. Originally the rivet heads were on the inboard side of the rib.

[cessna170bdriver]

…
And where can one source the fuel tank straps and the filler neck gaskets?

I replaced my filler neck gaskets last winter with the ones made of viton by RealGaskets of Tennessee. They are about twice as thick as the stock gaskets but that didn't cause any fitment issues. My AP/IA signed them off with a logbook entry. I’ve flown about 40 hours since then with no leakage.

[DaveF]

Go with Miles' recommendation for Viton gaskets. Now that you're down this rabbit hole you only want to do the job once.

The first time I resealed mine, I made seals from cork/rubber gasket sheet from Napa and sealed them with Permatex no.2. Lasted about three years, then failed. The cork shrank and hardened. This last time I bought the gaskets from McFarlane and sealed with EZ Turn. Only later did I find out that the Viton gaskets were available. No leaks so far, but next time I'll use them.

Just as important as the gaskets is sealing the six screws that hold the filler neck to the tank. If they're not sealed you'll have a leakage path from the fuel tank to the filler neck moat. I used Proseal on the threads and under the screw heads. So far so good.

Unless you're lucky and the old in-tank gaskets peel off cleanly, scraping the old ones will cause a lot of bits to fall into the tank. The only way to avoid this is to remove the tank entirely from the airplane and flush the tank after scraping. That's a lot of extra work, but if you don't do that you'll be sumping little black bits for months or years. I've done it both ways. Luckily or unluckily, at least one of your tanks has to come out anyway.

[ghostflyer]

I found all my straps broken and it appeared that they had been broken for many years by the marks inside the cavity . However found one wing on the interior surface the lower surface of the wing skin ribs had a plate riveted over then. Same as a later model 172 with tanks] The other wing ,well the tank had nothing to support the tank except the undersurface skin of the wing. These were not the original wings from production.

[Bruce Fenstermacher]

Go with Miles' recommendation for Viton gaskets. Now that you're down this rabbit hole you only want to do the job once.

Viton was not available when I created the gasket templates years ago. I'd go with Viton if I had to do the job today.

[n2582d]

I too like the idea of Viton gaskets but, considering that “akclimber” presumably has his plane based in Alaska, is this the best choice for the cold climate there? Suppose it might depend on where in Alaska he’s based. Viton’s lower limit is -15°F. Thinking of the Challenger accident attributed to Viton o-rings leaking with unusually cold weather.

[Bruce Fenstermacher]

I too like the idea of Viton gaskets but, considering that “akclimber” presumably has his plane based in Alaska, is this the best choice for the cold climate there? Suppose it might depend on where in Alaska he’s based. Viton’s lower limit is -15°F. Thinking of the Challenger accident attributed to Viton o-rings leaking with unusually cold weather.

Well it's taking a while but Gary wins the prize for being the first to link a 170 operation to the Space Shuttle.

[GAHorn]

…
Well it's taking a while but Gary wins the prize for being the first to link a 170 operation to the Space Shuttle.

Don’t forget TIC170A Member Earl Eastabrooks, Shuttle Simulator Instructor.

[akclimber]

Thanks for all the replies and ideas!
Hopefully I don’t have to replace the tank gasket, but possibly only the wing skin to filler neck gasket. That one doesn’t appear to be that critical since it only keeps water and spilled fuel from getting under the wing skin. And my strap is broken at the tightening bolt, so I should be able to just rivet on an extension to the strap and not have to remove the tank.

[cessnut]

While you are in there grab a mirror and look closely at the front spar top cap where the nutplates are attached, and between the extruded angle and spar.

[GAHorn]

While you are in there grab a mirror and look closely at the front spar top cap where the nutplates are attached, and between the extruded angle and spar.

Yup!

IN fact,…WHENEVER re-fueling…. take a CLOSE look at the line of rivets in Front of the gas-cap where the leading-edge skin overlaps and joins the spar-cap. Look for “bumps” …. an area between rivets that “rises” …where the skin rises between the rivet-heads. If you observe that… you likely have spar-corrosion… and that is seriously needful of being addressed.

[n2582d]

Behind the wood blocks (p/n 0253254) is another place to check for hidden corrosion. See this thread. The same issue was described in the following Service Difficulty Report (SDR) on a C-150.

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