The culprit plug is the main oil galley plug. Its above the rear main seal and is not related to the rear main seal in any way as shown in TXE36's photos above. Its got a composite washer/seal that needs to be replaced. Its the huge threaded plug shown in the picture above that takes like a 17mm hex key if I remember right and looks just like the drain plugs on a transmission or differential so anyone not familiar with it might have thought it had a copper crush washer under it and might not have thought to replace the composite washer/seal while they were in there. But if it were leaking before the rear main seal replacement, then it would have been obvious because there would have been oil on the engine casing above the rear main seal. I found mine was barely finger tight and that's why it was leaking, and quite badly. I could find no official torque spec listed for it but I set mine at like 25 or 30 ft/lbs. Your main seal did not need to be done over again so soon if it was not leaking but 90% of the cost is removing the transmission and getting to it. The main seal itself is only like $30. It could very well be just be bad luck combined with a shop or mechanic who was not experienced with this engine not knowing to go ahead and replace that $3.50 composite washer/seal under the galley plug as a preventative measure. After all, it is now getting to the age that seals like these start to leak.

 

Hi, Phil: Thanks for your quick reply.
If I understand you correctly, you have to drop the tranny to get to that hex Plug / Bolt which seems to be a very common leak problem.
An experienced jag mechanic would have changed that while he was doing the rear main seal especially if he was asked to locate and fix all oil leaks.
So it seems I am paying for their learning curve!
If it is not a freeze plug I wonder what the hole is for.
Maybe the motor was suspended using that threaded hole during manufacturing?

Thanks Again
​​​​​​​GreggP