[Clutch Cargo]

When I picked up my MINI, the salesman pointed out a "pfft" sound as he undid the gas cap. Since then, the gas gauge has read dead empty (except on two occasions when it seems to have worked perfectly ). I watch the trip odometer and gas up every 250 miles, but I have never again heard that "pfft" sound. The dealership told me that it was a faulty sending unit and have ordered a new one, but I wonder if a faulty air seal could be causing my problem.

Do you guys hear air hissing into the gas tank 1)Always, 2)Never, or 3)Only when it's quiet?

[AidenL]

So far, I have never heard this, I must admit, maybe I'll rephrase that.........I've never noticed it, must keep an ear out next time......

[Fullonloon]

It's just the release of gasses when you break the seal on opening it after driving. It's perfectly normal. Had it on most turbo cars and on my cooper. No worries.

[Basil]

1) Always

Optimax makes it Pffffffffffft rather than Pffft.

[Martin L]

Always.
Had it do that on all cars I've owned as far as I can recall.

[Clutch Cargo]

Thanks m8s. If you hear it all the time, I should hear it at least some of the time. I shall bring this clue to the attention of my dealer.

On my older cars, I only ever heard this noise when refueling on a long road trip, due to the vacuum left by the recently-consumed fuel. But it was explained to me that the MINI has modern negative-pressure gadgetry in the fuel tank to reduce emissions. So it makes sense that the "pfft" should always be heard. If a vacuum is needed for the sending unit to work properly, replacing it won't fix my problem unless the seals are repaired too.

[erazo]

If there were a problem with the seals causing a loss of pressure then the "SERVICE ENGINE SOON" (or engine graphic in CA) light on the tach would illuminate.