thermostat problems
 

my 1997 eclipse has went through 3 thermostats in 4 years. the last one went bad in Oct. 2004.
now it is broke again.
the only way i have known that they were bad is becouse the car will run cold when i am on the freeway. It runs at reg. temp. when sitting still. has anyone else had this problem?
does anyone know what could cause the thermostat to keep breaking?