I replaced the thermostat on my 95 xj 4.0 along with other items because of overheating. The first time around it leaked at from the housing at the bottom bolt. I thought ok I did something wrong so I got another gasket and did it again. Again it leaks from the same spot. Long story short Ive done this with a gasket and gasket glue, with no gasket and just glue and all of them above, every time cleaning thuroughly even buying a new housing. Is it possible that the head is sooo warped that it leaks like that but will still run fine?

 

You got a new housing? I would try and put a strait edge on the housing and then on the head and look for a problem

 

I'd be pretty surprised to see warped housing. It's happened, but not often. Like 91 said, take a straight edge to both and find out. More than likely, it just has some crud on either the housing or block that's not letting it sit flush. take your time cleaning both off with a good gasket scraper, use a new gasket with some RTV blue on both sides and tighten it up. If it still leaks out, make sure the bottom bolt is tightened all the way.

 

O and tighten the bolts evenly. Dont just tighten one then the other.

 

I would make sure the surface is dry as well, when I did mine there was a little bit of fluid that kept dribbling down the lower part of the mating surface. You can either jack the front end up a bit to keep it from leaking or soak some of the anitfreeze up with a shop towel. I also let my RTV cure a bit for 20 mins before filling with fluid again