What is this plug in my engine block?

[samuelLJ]

Replacing my oil pan, RMS, and some other things while the pan is dropped. I was about to start putting the pan gasket back on when I noticed this, what is it? I couldn’t find it anywhere in the 2004 parts diagram in any of the engine drawings. 2004 LJ 4.0

 

[06lj]

I'm pretty sure that is just for positioning the block during manufacturing. You will find another hole on the front of the block below where the alternator bracket is. As long as the plug is still in good shape I wouldn't worry about it.

 

[samuelLJ]

I'm pretty sure that is just for positioning the block during manufacturing. You will find another hole on the front of the block below where the alternator bracket is. As long as the plug is still in good shape I wouldn't worry about it.

Thanks for the info. It doesn’t look excellent, but if it doesn’t matter and I can’t even find a part number for it, I’ll just leave as is.

 

[Jeep&dog]

As I recall there was a Technical Service Bulletin (TSB) out regarding that hole. The rubber plug in your photo was the solution called for in that TSB, which was intended to prevent premature rear main seal wear. I don't have access to look it up the at the moment, but if there is even a slight chance that piece of rubber delays a RMS replacement, I would definitely leave it where you found it!