My neighbor owns a 5.2 96 Grand Cherokee Limited. He had a leak in his coolant system and we noticed no coolant going into the radiator so we replaced the thermostat. We used a gasket and it was leaking so we placed sealant on both sides of gasket and allowed to dry. The coolant blew thru the gasket and sealer (grey thermos housing sealant) . We took it apart and cleaned the engine block and housing with sand paper and cleaned with break cleaner and allowed sealant to sit over night. we just cranked it and all was well till the temp got to 210 and then the coolant blew out the seal around the thermostat housing again. We called parts store and they said housing might be warped and we ordered a new one. this housing is a vertical mount on engine and not the one coming from the side. Does a warped housing sound like a probable cause?

 

Your 5.2L uses a thermostat housing that is nearly as thin as sheet metal on the base, and warps easily. Place the old one on something perfectly flat, like a mirror or a piece of window glass and see if it "rocks" when wobbled sideways. It shouldn't, and if it does it needs to be straightened or replaced.
Place the t-stat in the machined groove in the manifold. Apply a thin, uniform layer of RTV to both sides of the gasket and place on top of the t-stat. Install T-stat housing and bolts, and tighten to 16 Ft.-lbs only or warpage could occur.
Re-install hose, and clamp.
Refill cooling system, and check for leaks.
Hope that's helpful.
And Welcome to CF.

 

will test flatness of housing. appreciate advice

 

Just trying to help.