8

When I fill up with fuel, there is often a loud hissing noise, as if you are opening a bottle of fizzy drink or something whenever I unscrew the petrol cap.

It also seems like there are vapours rising from the hole, as there is a shimmering shadow from the tank.

What is the cause of this?

Is this a problem?

Does this mean my fuel tank ventilation valve is broken?

I have a 2003 Opel Agila

George
  • 6,605
  • 38
  • 86
  • 123

1 Answers1

13

Regulations limit the amount of unburnt hydrocarbons that can be released into the atmosphere, therefore fuel tanks on cars now have to be sealed to stop these emissions. The noise you hear is air rushing into the fuel tank, due to the low pressure caused by the use of fuel.

HandyHowie
  • 25,681
  • 3
  • 40
  • 76