The gong is mounted on the under dash trim above the passenger footwell. If your sound like a loud BONG is from the rear, its could be the fuel tank not venting properly, as is a common problem. However it needs attention quickly, as the bong is caused by a partial collapse of the fuel tank, which then leads to failure of the seams, leakage and £££. It seems to be difficlut to isolate the actual blockage, so some resort to drilling a hole in the fuel filler cap, and if this is done at the opposite end from the retainer strap, it will point down, avoiding rain getting in