I would change the thermostat and check the thermostat housing for
any obstructions. I believe your temp spike is due to the thermostat not
opening properly and you get a momentary steam pocket at the sender.
I prefer to use a 180 degree thermostat. Ford engines are designed
to have less internal wear when the operating temperature is in the 180
neighborhood. Also living in NY State I prefer to have good heat for the
cooler night we get.
The temp sender is on the intake manifold (Tiger). The thermostat is a
160 degree piece. I'm not sure how or why an air bubble would just set
itself under the temp sender though.
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.543 / Virus Database: 337 - Release Date: 11/21/2003