We have the Taurus, and every so often, I would say 1 time a month, it blows it's overflow cap off! We have changed the head and head gasket, installed a new overflow and numerous caps,tried 3 new thermostats, cleaned the cooling system, flushed the cooling system and made sure it is full. Now, the head we put on was used but looked very flat and smooth. We are just stuck as to what could be causing this. The fans do work and they kick off and on like they should. The temp gauge in the car sits right mid point as it should. Please.. HELP!!!! Thanks!