I take it the seams gave way somewhere?

...that your cap is venting properly? I have seen this happen to tanks when the vent hole in the cap is plugged up with gunk. Pressure builds up and it needs somewhere to go. That said, if the vent hole in the cap is the problem, your tank may still not leak at the seam if you fix the venting problem. I think that the added pressure causes the seepage, not the static pressure of the liquid.Bilko wrote:Just to confirm, I've sprung a leak and I found this pool of petrol sitting around the seam of the tank. Everywhere above the seam on the tank is dry. There's a fair bit leaking down the inside of the casing.
I take it the seams gave way somewhere?