Just replaced a busted freeze plug between the tranny and engine, then it started leaking from there again. Just pulled the tranny back off and my freeze plugs are fine, its actually pooling up between the pan and the block at the oil pan bolt right next to the rear main seal. Is there a coolant passage under the oil pan by the rear main?

 

Look up. It might actually be leaking up higher/forward, and dripping from there as it is probably a low point.

Another freeze plug(s), head gasket, cracked block, cracked head, heater hoses/fittings, etc are all possibilities and need to be verified or ruled out.

 

Check your oil for coolant.

 

The cylinder head has a freeze plug at its rear.

 

Blowback from a leaky water pump?

 

older XJs have a sender for the temperature gauge at the top-rear-left of the head, could be leaking from there, or from a freeze plug at the rear