I took out my thermostat housing after being told by a shop that it was leaking. I replaced some of the gaskets and bought a new housing but didnt put it in because i was in a rush and it didnt seem like it was going to fit. It drove over 160 miles and almost no change whatsoever in fluid levels but there is still a little bit of fluid leakage on the housing its self. The top piece of the housing was not replaced and from what i read online that is where the leaks happen. But after tightening all the bolts there is no leaking coming from that area. the only leak is coming from the hose next to the thermostat electrical connection. Also, there is a lot of fluid build up on the block of the engine where the bottom of the housing screws to the engine but it isnt going away. I can provide pictures if need be. Will be putting the new one in this weekend hopefully.

 

If it's a 4.0,this is a common failure. Check out the all metal aftermarket solution

https://smile.amazon.com/gp/product/B00G9AYWRM

 

It sounds like you're already keeping a close eye on it, and planning to replace it. Those would be my 2 recommendations.

I got just a little over 10 years out of my housing, but many others weren't that fortunate.