How do you know your thermostat is bad on a ford Taurus 2003 model?

Answer 1

You can test it by squeezing the upper hose as vehicle warms up. When it opens more will flow through the hose-enough to feel the difference. .....................................................................................................................................................

Also, Watch the temperature gauge. If it rises to the red "warning area" then the vehicle is overheating. This is a sign of a stuck closed thermostat. Most vehicle come equipped with a fail-safe thermostat that will stay in the open position though if it were to fail. If this is the case, the vehicle heater will seem like it will blow much colder on cold days. Also, if it is stuck open, your temperature gauge will read lower while driving than while at idle.

If it is overheating, you will also want to check your coolant level first. Also check your belts and your water pump. Strangely enough, low coolant level is the cause of most overheating problems. Good luck.