I've got some experience with Excels having owned 3. First, the most likely thing that happened was the tank flusher was left running with the black gate closed and it overfilled the tank. This unit will split the seam out near the top of the tank (especially with age). The bad news is that on these earlier year Excels the tanks (black and grey) are no longer available and the fix is to go to a later model tanks which requires refabricating the mounting hardware that retains the tanks. It requires both grey and black tanks be replaced as a set. A friend just did that at the tune of $2,600. If the tank is split at the seam, repairs to the tank are not viable. Sorry to be the bearer of bad news, but had to share my experience on this subject. rockin'