how can i tell if i have a blown head gasket? its a 25 kolher. has no power loss. runs fine. had gaskets replased last year.(thats what dealer said ). i have a great dane chariot. the oil spot is right by the exsaust pipe next to muffler like wear the gasket is its on the head and the jug . i did steam clean it but its back .icant tell why its there again. the numbers on motor is the good numbers(serial#). it has 150 hours.