Recently, I replaced the thermostat on my 2.3L and replaced the badly rusted housing. Got it all back together and to my frustration it was leaking at the new gasket!! so I tore it all apart again, cleaned some more at the opening at the engine block so that I was as sure as I could be that there was no debris that could cause a leak. I also started with a new gasket, coated both sides of it with blue silicone sealant, and had a mechanic look at my new thermostat and housing and make sure that the new setup was correct. Got it all back together, let it sit 25 hours without fluid for the silicone to dry, rechecked the bolt torque so it was exactly to Chilton specs (19 ft.lbs), and it still leaks, but just enough to make a little "drool mess" around the housing. I'm beginning to think maybe the new housing is warped. Does anyone know if there's a way to check for this? it's leaking slowly enough that it doesn't appear to be losing fluid, it just smells a little bad.

 

Check the hoses that distribute the coolant in and or around the housing...Ive noticed the clamps around my housing rub against other hoses, and create a small leak that only appeared when the engine was hot enough and the stat opened, which was also disguised by the heaer core hose directly over it.

 

Had the same issue with mine. I replaced the gasket 3 times doing different methods of sealant and no sealant. I ended up putting a good layer of sealant on both sides of the gasket.