Fuel hoses for the vapor recovery system

[RonDwyer]

Well, it's getting close to completion. There's just so much I can do to get it ready for the referee. Wiring is complete, got a 179 ECU that makes it run so much better than the 150 unit. Changed the sending unit seal on the gas tank. I need to have the custom pipes brazed to the muffler, I cannot seem to clamp them tight enough to seal up.

Smog referee seems more hung up on failing me for a pin-hole leak in my vapor system than my fresh B34 with cats & lambda. Something the prehistoric 530i with thermals, air pump and prehistoric L Jetronic never had. I'm guessing the hoses back on the filler neck all should be replaced as well as the rubber intermediates on the way to the charcoal cannister.

I know silicone hose is bad for fuel systems, is it bad for the vapor system as well?

Have to see how this one progresses.

[Mike W.]

I'm not surprised they got testy about vapor emissions, about 10 years ago they really tightened that one up. Regardless, if silicone isn't fit for liquid gasoline, I don't think it would fare well for vapor gas either. I'd just go with plain old rubber, it lasts 15 years or so and it's cheap. I don't know how different the earlier cars are, but for later ones I just get 6 feet of each 6MM and 8MM and have a little left over. Or 1/4" and 5/16", that's close enough too and sometimes easier to find on the Sunday afternoon I usually seem to find myself doing it on.