If its a zetec motor get the stat out and get a new one about £10 but when you get it out have a look at the housing as they melt inside and it lets the water pass the stat if it has gone you can get the housing from any tat yard there are about 2/3 tipes of them but there on the 1.6 / 1.8 / and 2.0 all so dont forget there on mondeo,s as well