I pulled a few pistons, and got to the third one. The rod nut would not break loose. Turns out that the bolt is turning in the rod! The bolt depends on a tight fit to keep from turning. There is not flat or other solid mechanical means to positively keep it from turning.

I'm amazed that MB would do something like this. These engines are typically long lived, so I guess most folks don't run into this.

What are my alternatives? I obviously have to get this nut loose. I hate to wreck the rod.

Any similar experiences and solutions are appreciated.

Have a great day,

I would probably burn the nut off with a torch, but a carbide wheel would also work. Usually an air wrench will get them off with a little holding of the head with a pliers or screw driver.

Larry,
If you want to save the rod try to avoid heat. Get an appropriate size nut splitter from NAPA or the like. Thanks for all the wisdom and insight you've shared in the past.

Bob D.

Heat the nut with a torch or lighter, cool the bolt with a piece of ice. The nut expands and the bolt shrinks - not visibly, but perhaps enough to put it over the edge for that first little turn.

- Nathan