When I remove the petrol cap there is a rush of air into the tank. Do I need a new petrol cap as there appears to be a one way valve in the cap that may be sticking. Alternatively does the tank have a breather pipe, and if so where does it terminate?

 

------------------

 

are you sure it was in and not out?

Whether it's in or out, I cant remember what it is, its perfectly normal.

The tank is presurised.

 

Stuart

I have just checked the car and it is under pressure not vacuum. Is this normal

Yes. The Owners manual suggests opening up 1/2 a turn to release the pressure and when the hissing stops open up full.

 

The manual goes on to explain that the cap contains a safety valve and so must only be replaced by a genuine part.

 

Zimon

Whats the point of it bein under pressure?

 

One possibility is that it pressurises (or doesn't vent pressure) to stop the lighter fractions of the fuel from evaporating. Its the lighter fractions which give petrol its petrol characteristics - this is why old fuel makes the engine difficult to start....

 

Just a thought....

 

CheerZ,

 

Andy

I reckon it's so that it squeezes even more fuel through and so empties your tank even FASTER!!!!!