View Full Version : Leaking O ring

03-08-2016, 06:45 PM
This is the connection between the gas tank and fill tube. Three tries and I still can't get it to not leak. New tank and new fill tube.

The first time was mine using an O ring from Macs. Leaked. Then I bought a Viton #328 (1-7/8" ID x 3/16" thick) and buddy Joe installed it (very experienced). Leaked.

Then I tried again with a thicker O-ring #404 (1/4" thick) and the fill tube would not go in using a wood block and small hammer. So I greased up another #328 and pushed that in. Still leaks.

I can see the gas dripping when the fuel level is above the bottom of the connection. No leaks when the fuel level is lower and sitting in the garage. When the level is down it leaks when I drive due to fuel sloshing.

I need to fix this before I have a fire. Any advice appreciated!

03-08-2016, 06:57 PM
...So I greased up another #328 and pushed that in. Still leaks...Instead of using grease, why not use gasket sealer like Permatex BLACK?

03-08-2016, 07:22 PM
Instead of using grease, why not use gasket sealer like Permatex BLACK?

That's what I would try. You can also try soaking it in some brake fluid. That may cause it to swell up enough to seal.


03-09-2016, 08:57 AM
The Permatex black doesn't say anything about resistance to gasoline, just oil. Is that the best product to use?

03-09-2016, 09:03 AM
I'm thinking of this stuff: http://www.amazon.com/Seal-All-380011-Seal-All%C2%AE-oz-Adhesive/dp/B0000AXYZG

03-09-2016, 09:24 AM
This is probabaly a lot better: http://www.permatex.com/products-2/product-categories/gasketing/gasket-sealants/permatex-permashield-fuel-resistant-gasket-dressing-flange-sealant-detail

03-09-2016, 10:28 PM
I replaced my fuel tank and filler neck and gasket 3 years ago.

The one that came with the filler neck would leak when the tank was full or if I parked the car on an angle or when the car was jack up.

I bought a new filler neck o ring from Pat Wilson's. It was thicker than the one that came with filler neck. I checked for rough edges on the tank and on the filler neck. Then I put vaseline all over the gasket and installed it. It has not leaked in 3 years. My car get driven almost every day. It could be the vaseline lube it up so it slide into the correct position or it filled the small imperfections in the metal.

Could your leak also be caused from the fuel injection system creating more pressure in the tank or not venting correctly?

Thank you for sharing your problems and solutions with us. It has helped me.

Good luck. Your car looks great.

03-10-2016, 08:43 AM
Thanks. I just ordered a new O ring from Pats. Only $2 (but shipping was $18). I ordered new front shock rubbers (which I also need) and that lessened the blow a little.

These catalog shipping costs drive me nuts.

This connection leaks when the filler cap is removed, so no it's not a venting issue.

03-15-2016, 10:17 AM
Here's a photo of the three O rings. The one from Pat Wilsons in in the middle, and "standard" Viton O-rings are on either side. The ID of the center ring is slightly smaller, but I don't think that's the critical dimension. Thickness is.

Here's a comparison of thickness dimensions:

#328 labeled 3/16", decimal measurement .205", fraction 3.3/16", metric 5.2mm
Wilson's, decimal measurement .230", fraction 3.7/16", metric 5.8mm
#404 labeled 1/4", decimal measurement .265", fraction 4.2/16", metric 6.7mm

03-22-2016, 02:00 PM
I finally got around to replacing the O ring. Somehow I pinched and ripped the old one when I put it in. This time I coated the tank seat with Permatex, installed the ring, coated that with more Permatex then assembled. The fill tube slid right in without having to force it.

03-22-2016, 04:06 PM
Success! I filled the tank until auto-stop, and no leak. No stink in my garage either.

03-22-2016, 05:18 PM
Aah, you're a good man, Steve. Glad it worked out. Nothing is more dangerous than leaky gasoline. - Dave

03-22-2016, 09:08 PM
And stinky too.

But with regard to fire, it really got me thinking. I've been careful with my fuel system and mechanical modifications, but something can always go wrong. So I invested in 2.5# of Halotron and mounted it to the driver's door.