It only takes one gorilla with a 1/2 ratchet one time to warp a thermostat housing. Another way to destroy one is cut the ridge on the flange with a sharp gasket removing tool or a putty knife. It's only aluminum. Torque to specs and no farther. On used housings, I check it with a straight edge and inspect the ridge. If either check fails, I toss them. Why? because I know I'm setting myself up for failure. RTV is just a band aid for a boo boo. It will work in some cases, but why not do it right the first time.