funny noise from petrol cap

Replaced my filler neck about 3 months ago and have recently bought a new filler cap as my old one wasn't sealing properly and could smell petrol fumes 8O

Anyway i went on a run and when i stopped i could head a faint whistling sound coming from my petrol cap, upon taking the cap off there was a massive release of air  8O

Dunno if it was a suck or a blow though but nether the less slightly perturbed me.

Any suggestions?

Thanks in advance

P.s it's a 1992 1.8 clipper carb

mine used to do the same thing, i just removed the rubber seal from the cap, problem solved

chris

Sounds like the vent to the tank is blocked. Assuming the golf has one. Make sure the cap has its rubber seal on for mot time as its a sure fail.

Mine does the same and has done since I had it 4 years ago. Mines a GTI and there is a valve up by the filler neck which the tank vents through. I've recently had all the tank parts out and replaced the valve for another second hand one I had and it still does the same so not sure if the 2nd valve is faulty or is it that they just do it.
Maybe the valve only lets air in under negative pressure which would make sense in the event of an accident.
There's nothing in the haynes manual about it as far as I can see.

Interesting... mine does exactly the same thing. I replaced all last year - tank, filler etc Might try the cap seal thing over the next few days and see will it make a diff.

mines never failed on that?? must be being tested by Stevie Wonder lol

chris

Its positive pressure in mine. Its like if you have a gallon petrol can and half fill it with petrol then shake it up. It causes it to pressurise.

Why take the seal off the cap? Just to stop it making the noise?  :dontknow: It's never effected my engine performance so I don't worry about it.

Say worst case scenario and your cars upside down with you trapped in it. Your fuel will be pi**ing out if you have no seal on the cap.    :pray:

If it is pressurising then at least your filler necks not rotten!!

It's supposed to do that, the tank is designed to have some positive pressure.
There are two cap types, vented and non vented, GTIs must have a non vented one fitted. You will find "Ohne blau Lüftung" stamped on the metal part.

Mine has always done that,ive had it 18 yrs