To add to what Docfixit said:
It is on the drivers side lower side of block. You remove the alt. For access.
It is an assembly, that is, the thermostat and housing are one unit.
If you are getting a code for temp. Below thermostat threshold, then it may be the coolant temp sensor. GM has had a lot of problems with this sensor, and they are hard to get.
Sunday, December 14th, 2008 AT 6:59 AM