Where is the thermostat housing on a 1006 Buick Regal?

The thermostat in the 3.1 engine is in the thermostat housing. Follow the upper radiator hose towards the engine, where the hose connects to the engine is the thermostat housing which leads under the throttle body. Yup, it's not the easiest thing to get to unless you have small hands and a few socketextensions and swivel. If you have small hands you can remove the thermostat housing without removing the throttle body. Just remove cross over exhaust heat shield to give you enough room to get the socket with an extension and swivel to the two bolts to the thermostat housing under the throttle body. Remove front bolt and the second one just needs to be loosen and you can wiggle out the thermostat housing to replace the thermostat. If you need more room, your going to have to remove the throttle body and replace the throttle body gasket also to give you more room to get the thermostat housing out. Good luck and hope this helps and take care not to damage the temperature sensor on the manifold just in front of the housing. Keep me posted if you have any more questions and take your time.  

Follow the top radiator hose, it's connected to the housing.