Yep, you are on the right track. One causes the other.

 

I guess I was considering that after installing the new components (thermostat with new gasket and housing along with hoses and a new cap) it couldn't even heat up enough to open the stat when I was flushing it. It runs like an absolute champ, with the exception of a slight knock. Checked the oil and it is both low and old/black. No leaks and what was there had 40psi of pressure. Considering how I came across this XJ and the little work i've done so far, I'm a happy camper.

 

Good to hear! If the knock doesn't go away let us know. Maybe we can help pinpoint it to see if it is something to worry about or not.

 

If it's been sitting for 8 years I would change the water pump and thermostat .