Help appreciated

[Dave F]

My girlfriend has a 1200 corsa and it had a leak from the back of the fuel tank. I removed the tank at the weekend to find that it has caved inwards which I presume caused the split and the fuel leak. I have ordered the new tank but can anybody suggest why it has done this. My first thought is that a breather pipe is blocked as it is a sealed fuel system would this be one of the pipes going up to the filler neck and is there a valve up there that draws air in as petrol goes to the engine (possible blockage). Or could it be a problem with the vapour release valve and charcoal canister at the front of the car. Any ideas would be greatly appreciated as I dont want to remove bits that would have nothing to do with the problem.
Dave

[Soonto"HAS"soop]

how many pipes did you remove from it whilst you checked it?? Check all of those first.

[Dave F]

I removed three from the back of the tank one small one medium and one large these all go to the filler. then two small ones that come from the pump the feed and return I take it. There is also another pipe that goes from the filler towards the engine but this is still connected. I am wondering whether one of the three pipes from the filler to the tank is a breather (That may be blocked) that lets air in as the fuel is used. Please correct me if I.m wrong