Fuel cap gaskets

Cspeare

I read the past article on gas caps and purchased the new gaskets from Aircraft Spruce. I removed the screws then took off the old gasket that was not rubber. I placed the new gasket on the brass backing plate and reassembled the cap. With the thicker rubber gasket I find they are too tight of a fit and very difficult to turn and secure. I tried lubricating them with Dow Corning 4 dialetric grease but still too hard to turn the final twist to lock into position. I then shimmed out the cap with a couple of washers but the fit was too loose to seal the tank opening. I’ll try replacing the washers with a round piece of thin aluminum to match the shim that is under the cap. The shim thickness is critical to being able to secure the cap. Also I am not happy how loose and floppy the new gaskets fit the cap. Is anybody else having issues with new gas cap gaskets?

Scott Sherer

Hi, and yes. There are two thicknesses and I purchased the too-thick ones, also, to the same end as you. Get the thinner ones and they snap right on. You don't have to remove the screws, they just stretch and pop on.

arrow76r

Scott,

Are the correct gaskets the 1/16 inch type? (A/C Spruce # 05-18500)

Scott Sherer

There are two correct gas caps for the Arrow. One is the 66817-00 cap and it uses the 66815-00 thin gasket, listed as 05-18500 on aircraft spruce. The other is the 39830-800 cap and it uses the 39829-00 thick gasket.

arrow76r

Thanks, Scott. I will check which is the correct one for my Arrow.

Cspeare

Thanks Scott. I will look for the thin fuel cap gaskets. Thanks for your help.
Cliff Speare

Scott Sherer

Ok Cliff. Good luck!

arrow76r

I received my two gaskets yesterday from Aircraft Spruce. Too cold to mess with them today and snow forecast for the next 2 days.

Scott Sherer

Hi Jim,
Glad to hear that you've received them. Don't remove the screws on the cap, they just snap on and off.

arrow76r

I took one gasket off a cap to measure the inside and outside diameters and it was trivial to take off so I suspect the new ones will be a non-issue. I also got a small container of the "lube" just to preserve the gasket life. It is likely that my home base airport will be closed for upwards of 3 months this summer during which the one and only runway of consequence will be re-built thus leading me faced with moving to the municipal aerodrome (KCOS) and having to tie down outside (AUGH!). Hence my ordering new gaskets to keep rainwater out of the tanks.

Scott Sherer

Good idea, Jim. Sorry about your home airport being closed. Can't they do that in January? lol

joshuaboyd

On my 67 Arrow, the fuel caps have no visible screws (like the photo below) to take them apart. In replacing the gasket, does it just stretch around or do I (or my A&P) need to disassemble the cap first?

Unit74

It’s stretches over, carefully. I’ve pulled a few off over the years. Not a big deal at all.