If the vent is in the wrong place, move it? If a fitting is leaking, then you have to find the leak. Is the vented look cap on? (If it isn't ...

I don't think that the hose being pumped would generated that much instant gas from nothing -- i.e., permiated hose would me more continuious an in issue.

But Peggy's book (and past posts) have decriptions for checking hoses with plastic wrap, as I recall.