Odds are strong that it is the first rod bearing if it is a rod knock. Perhaps you might pass along that the bearing is replaceable. By removing the bottom section of the oil pan.


Depending on the condition of the journal it might be repairable in place. Not a strong chance but possible. You might want to pass this along to the purchaser.


I came out of the cottage on a nice sunny morning years ago. Fired up our 1979 300d only to hear a knock. Opened the hood and it was towards the back of the block.


It did not sound quite like a rod knock so I thought it may be the flex plate. Still I was not very happy. It was really pronounced.


Then it went away. So I thought what the hell. Maybe the starter drive did not retract far enough but that should have sounded a little different. Anyways it never reoccurred. Still wonder what it was anytime a post like this one comes up.


The miles accumulated since on that car it almost must have been the starter drive.


Or perhaps the engine just was afraid I would work on it and cleaned up it's act.