With the top of the housing off you can now see the thermostat and the ECT sensor that is underneath the housing. Notice the little bleeder/swivel valve on the top of the thermostat, ensure when you put the new thermostat in that the little bleeder valve is facing forward.

       Pull the old thermostat out and clean up the bottom of the housing. The ECT sensor connects to a bracket on the back of the power steering pump, just wiggle it off the stand off, and then unplug the sensor. The sensor is a 19mm, and is not on that tight. Make sure that when you are replacing the ECT sensor that the sensor comes with a new small aluminum crush washer.

       Above and below are pictures of the parts needed. Any Volvo store or various on line supply houses should be able to get you the parts.