Originally Posted By: Rick in PA
Originally Posted By: oldhp
Use the "Right Stuff" gasket maker lightly on both sides of gasket if leaking.
Flat sanding the housing and lightly flat filing the flange mount also help. Doubling the gasket works too.
Flat sanding is a good idea on aluminum housings. We use to do this at the garage I worked at as a young man. We'd take some sandpaper, lay it face-up on a glass counter top (any glass would do, it's a good hard & flat surface). And then gently "orbit" the housing on the sandpaper. It was interesting how the ears would generally brighten first, revealing a subtle warping of the housing. After a bit of sanding, the entire face of the thermostat housing would brighten, indicating the housing face was flat.
I'd be surprised that he would be able to sand it flat, because many Ford t-stat housings have a small bead cast into them in the middle of the sealing surface.
Still, you do bring a good point that many housings can warp and leak.