Check your gas cap o-rings

L

little wing

New member
On our last trip, the marina gas pump attendant noticed the gas cap o-rings were quite deteriorated. Both gas caps as well as the water cap looked the same. I'm sure these are original (2005) and it's obviously time to replace them.

NG_o_ring.sized.jpg

Replacements are 2/$12.49 at WM.

These are the same and available for $0.79/ea at Ace Hardware.

good_o_ring.jpg
 
little wing":16x80bwl said:
On our last trip, the marina gas pump attendant noticed the gas cap o-rings were quite deteriorated. Both gas caps as well as the water cap looked the same. I'm sure these are original (2005) and it's obviously time to replace them
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Also, any hydraulic shop will have these CHEAP.
I picked up 10 for $2.00 a few years back. :thup
 
Great reminder, and I have been eying my O rings on both the fuel and water caps. You want to be sure that the "O" ring is resistant to gasoline for the fuel tank. Also resistance to UV and Ozone is important. I tend to favor FKM/FPM/Viton™ (Flurocarbon) over the "NBR" or Nitrile O rings. Any "rubber" which is not one of these is probably not the best choice for longevity in the fuel environment. Ethylene-Propylene / EPDM:is not resistant to gasoline. The Vitron is going to be a bit more expensive. On the other hand, West Marine charges $12.95 for two "Perko" O rings which are listed as "rubber". Wholesale Marine has "Sea Dog" O rings for $1.27 each...but again don't list the composition of the material. Grainger has the 1 5/8 OD in Nitrile at about 10 cents each, Viton for about 40 cents each, and Silicone for about 20 cents each. These prices are all in packs of 25. Can you say "marine markup"?

I like to keep my fills clean and a light coating of "Superlube O Ring silicone Grease" on the o rings and threads.
 
According to the Danco website the #50 o ring is made of "Durable rubber construction". So is nitrile a rubber? Not trying to stir the pot, just trying to get a gas resistant o ring.

Jay
 
A nitrile is any organic compound that has a −C≡N functional group.[1] The prefix cyano- is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, including methyl cyanoacrylate, used in super glue, and nitrile rubber, a nitrile-containing polymer used in latex-free laboratory and medical gloves. Nitrile rubber is also widely used as automotive and other seals since it is resistant to fuels and oils.
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It is a vague description on their website, though.
 
Description of Danco #50 O ring:

Made from Buna-N rubber to provide superior resistance against abrasion and water swell.
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Buna N rubber is Nitrile. So Little Wing is correct that the O ring is Nitrile.

"Rubber" is a bit ubiquitous (a polymer with viscoelasticity) --we normally think of "rubber" as a material made from Latex, and a natural rubber. However, Many items are also described as "silicone rubber", Neoprene Rubber, "EDPM rubber" or "nitrile rubber". The latex product from a plant is more likely to be described as "natural rubber". There can also be some synthetic compounds described as Latex.
 
Old thread:

The o-rings pictured above do fit the water & waste caps but both our fuel ones are much larger & thicker. I'm going to try to find them at Ace also so I don't have to pay $6 each.
 
I had a great experience at O-Rings West in Lynnwood. Although clearly geared as a commercial wholesale supplier, they took the time to analyse an old o-ring and sell me two new ones for a dollar when the OE supplier wanted $30 each.

Based on what I learned, I recently measured and bought a "kit" for rebuilding my vintage Wagner 701 hydraulic steering. $4 at Ace instead of $29 for the increasingly rare "official" rebuild kit (which does include a paper gasket). I just happened to have a "ring mandrel" from another project that really helps quickly measuring ID on smaller o-rings. OD is simply adding twice the o-ring thickness measured with a caliper. Easy peasy.

The most difficult part was that the little bins at Ace were a mess based on customers mixing up the sizes (plus metric mixed with imperial). I lucked out after close examination, but I should have taken the mandrel and caliper to the store. That would have saved me 10 minutes of tedium.

Mark

https://www.amazon.com/Rosenthal-Collec ... HY6BKTZ1DX
 
journey on":2jgsnf0i said:
OK, I'm confused. What are the O-ring OD and ring thickness? For both the water and gas caps.

Boris
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Boris, I'll go take some pics of what we have. The #50 o-ring (pictured in this thread) did fit our WATER and WASTE caps, but are too small for our GAS caps.

I just posted pics. The GAS caps are just larger and thus, so are the o-rings. The GAS o-rings look to be ~OD 2" ID 1 3/4".

This one will fit: https://www.danco.com/product/100-o-ring-1-per-bag/
 
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