so after 24 years i decided to do a full coolant flush, long overdue... so there was no way of getting it clean without removing the thermostat and stick a hose in the block.... the worst brown crap you'll ever see... changed the thermostat, put it all back together. it leaked, somewhere on the bottom of the housing near where the heater return hose. replaced the 5" return hose, got a new gasket, applied the silicone even more carefully, finger tightened, let it sit several minutes, then torqued to spec. and soon after, it's leaking again from what appears the same spot. ive done this job before without trouble, didn't notice cracks anywhere, anyone got any tips?