i'm in the process of replacing the head gasket on my 1991 300 2.5l diesel and what a job/nightmare ..... for 200K miles the motor looks amazing good .... NO ridge on piston walls cant feel one @ ALL vales look good and not burnt .. i have heard on some motors to use only new head bolts becuz they stretch ...is that the case on mercedes diesels, anyone know ....i have to replace a few becuz stripped head ... other than that any suggestions BEFORE I PUT IT TOGETHER ???