I got a call from my neighbour today advising me that my girlfriends car (Mk IV Fiesta, 1.25L petrol) was leaking petrol... from the filler cap.
I couldn't get my head around how this could be, not unless she'd filled it right to the brim (it had been filled only at the weekend) and perhaps today's sunshine had increased the pressure such that it was now overflowing (to the tune of a drip every few seconds). But then it would really take some doing to fill it that much... right?
So, when I got home I removed the filler cap and indeed found the petrol level to be right at the top... I wondered if the camber of the road had anything to do with it so replaced the cap and drove to a flat spot. When I got there I checked again and the level had dropped (completely out of sight in fact) and so I returned to the original parking position... and the petrol was still nowhere to be seen.
I wondered if perhaps something had blocked the filler pipe and managed to keep the level high? And perhaps this blockage was now in the tank? But then surely this would have posed difficulties when she filled it... and the receipt shows a full tank (~30L) was I'm not so sure about the theory anymore...
I'm now thinking more along the lines of a trapped air bubble? (I notice the filler pipe travels vertically down from the opening for around 8" and then horizontally for perhaps 20" to the tank. There appears to be two pipes to the filler - I don't know where the other goes (/comes from).
Any ideas? I'm losing hair scratching my head on this one so your thoughts would be much appreciated!
Incidentally, for what it's worth, the filler cap is a lockable aftermarket affair - when we bought the car a few years ago the cap was found to be one of those temporary push-in affairs. Also, we occasionally smell petrol inside the car (in the boot mainly, near the filler) and this is usually shortly after filling the tank. I've always put this down to sloshing fuel in the tank/filler and the likely less-than-perfect fitting of the aftermarket cap (whose gasket I see is starting to perish) which might be letting the occasional splash out to the surrounding area.
Mathew