Mark, For Thermostats I always use Ultra Blue silicon. Works great. Never leaks. Dan Nees cookiedan@domain.elided The "Good" 1979 Scout II 345/auto The "Bad" 1971 Scout II 304/T-18 And the "Ugly" 1979 Scout II 345/auto http://members.tripod.com/~IHCaholic/scoutindex.html