Fuel cap gasket... expanding? (TDI)

[hillstrubl]

In the quarantine I've driven collectively about 50 miles... so my 110 just sits. I took it out today and noticed something weird. The cap (~3 months old) gasket has pushed itself out past the plastic of the cap itself, its prob 25% larger than the diameter of the cap. Taking it off, I didn't notice any pressure relief but Its got to be that right? Yes, I should have included a pic.

 

[Napalm00]

Unsurprisingly the rubber in my aftermarket cap was also not fuel resistant. I replaced it with one cut from viton sheet, got it on amzn.

 

[hillstrubl]

Unsurprisingly the rubber in my aftermarket cap was also not fuel resistant. I replaced it with one cut from viton sheet, got it on amzn.

Yeah, I think that was exactly the issue with this one. I was able to salvage the old gasket from the cracked non-locking old cap.