Hello all,
I've had my 69 mach1 for 15 years now, and I just noticed for the first time this weekend a hissing sound coming from the gas cap after parking the car coming back from a normal Sunday drive. I popped the cap open, seemed to let the air in, popped it closed, hissing sound again. My immediate thought was that the round 1/8" thick (cork?) gasket that is supposed to seal the cap-to-fuel line had dried off and needed to be replaced. But after I searched and did not find any such gaskets for sale anywhere (I only found whole gas cap units that include the said gasket, but my unit is otherwise in perfect shape so does not need to be replaced), came these 2 questions : 1- I don't know much about air pressure in fuel line, so is that gasket supposed to be air-tight or instead that hissing sound is normal and I just never noticed it before? 2- if it is indeed supposed to be air-tight and it does need to be replaced, where can I find such a gasket? Ford? Autozone? NPD? Part number please? Thank you