Soak the temp sender with some penetrating oil like PB Blaster or Kroil, and gently shake or twist it as close to the cylinder head as possible. The capillary tube is very fragile, so proceed with extreme caution. There are no shortcuts- - - -just be patient and work carefully. Once the sensor is out of the head, you can check its operation with a pan of hot water and a candy thermometer, etc. to check its accuracy. If the radiator isn't boiling coolant out, it's probably not as hot as the gauge is indicating.
Jerry
