Fuel tank lock ring troubles

[ReticulateSplines]

Does anyone make O-ring cord with a D-shaped cross section

Yes, they call them D-ring seals.

I am keeping tabs on this thread, as there was a poor install done to my setup and I have not had the time to lift my bed/toolbox to tackle the job. I was also fairly certain there would be some troubles, not unlike yours. Most of the crummy workmanship I have had to redo lately has been that way.

 

[DrCharles]

Everything I found so far has been shaped like a D, but a round (or square) cross-section. I want the opposite (a circular ring but with a D cross-section), even in cord stock. oh well.

Meanwhile, the more I think about it, the more I worry that the RTV silicone will break down some day as the edge of it is immersed in diesel continuously whenever the tank is more than 2/3 full, and kept wet by splashing the rest of the time.

Hylomar and the Permatex version (available locally) seem to be the ONLY gasket sealants that are rated for gasoline and diesel exposure. I'm going to take the lock ring off again, and coat the sender flange, the exposed part of the O-ring and the cured RTV with the Hylomar. That should keep diesel off the RTV and everything dry. I hope.

I'm just tired of aftermarket parts being poor quality or defective right out of the box. But even if I were willing to bend over for Ford prices, not everything is available in Genuine Ford OEM parts for a 25-year-old truck.

 

[DrCharles]

This morning I bought some Permatex Permashield ("Compare to Hylomar Blue"), scraped off all the red RTV I'd put on yesterday, cleaned the flanges with brake cleaner, applied the sealant copiously to both flanges, waited a few minutes for solvent drying, pressed the O-ring into the groove and assembled. The Dorman lock ring is just a bit thinner than the one that comes with the tank and it was not holding the sender firmly with the slippery Hylomar. So I reinstalled the other lock ring and it tapped firmly into place. Then I siphoned the bucket in for the last time.
No leaks!

Finally I jumpered the electric lift pump and disconected the FSS, and bled the air out of the feed lines from both tanks. Road test successful. No leaks and no air when switching tanks.
A couple of good used bed bolts arrived in the mail today... now if I can get the bed back on before it rains...

 

[chillman88]

Glad you got it fixed! I bought a tube of Hylomar online and I've been using it quite a bit. Most places I'd normally use a thin smear of RTV now get Hylomar instead. It's supposed to be easy to clean off too but I wouldn't know since it hasn't let me down yet!

 

[DrCharles]

I also mail-ordered some too. 100g (3.5 oz) tube for $10.85 shipped. Definitely a better buy than 2 oz. which cost the same locally! It has a nearly indefinite shelf life, too, unlike our tubes of RTV which always seem to have hardened between uses...

Next test will be my leaking passenger-side valve cover (even with a new gasket), once I figure out how to snake it out of there. Gorilla at the shop who replaced the heads overtightened the lower front bolts in an attempt to seal it, which never works on stamped steel covers because it warps them further.

 

[genscripter]

I would think permatex sealer would also be a little bit more resistant to the fuel than silicone. I do not know how silicone reacts to diesel fuel, but I know it turns to a slimy goo when it gets against gasoline.

I agree. There are permatex varieties rated for fuel, that would be much better than silicone

 

[DrCharles]

I agree too. I take it you didn't see (my) posts #17 and #18 above