A system and method for testing and maintaining a power assembly of a locomotive diesel engine. In one embodiment of the invention, the testing apparatus comprises: a first test position for securing a strongback of a power assembly; a second test position for securing a cylinder head of the power assembly; and a third test position for securing a cylinder liner. In another embodiment of the invention, the testing method comprises: securing a power assembly to a first test position; removing a cylinder head from the power assembly; securing the cylinder head to a second test position; removing a cylinder liner from the strongback assembly; placing the cylinder liner into the third test position; cleaning the cylinder liner; testing the cylinder head for possible leakage; and re-assembling the power assembly cylinder head passes the leakage tests.