the thermostats in the newr trucks are not like the older ones. they have a by-pass. the one in my 2004 colorado works one day and not the next. it will cause the check engine light to come on if it doesn't work for a while. my truck runs alittle cooler when its not working and it never gets hot. heater puts out more heat then i need even when its not working. i've been running it for over a year and i see no different in the way it runs.
