This is a step by step for replacing the thermostat housing (and thermostat) for a 2005-2010 v6 4.0L Ford Mustang. Also, there is now an aluminum thermostat housing/water outlet available to replace the plastic thermostat housings. Whether you are installing a plastic or metal housing, this video aids in the installation. Both types are the same install process shown in this video.

I'm not affiliated with the company that makes the aluminum ones but I have found these on Amazon and eBay. I prefer them because I have had 4 plastic ones leak on the same car and was glad to find an aluminum part that will hopefully solve the problem.

let me know if you have any questions and I will do my best to answer them.

Tips:
--Assemble the upper and lower housings together with thermostat in place. This helps insure a strong seal at the base.
--Use a gasket making material in addition to the bottom o-ring because this o-ring can become flat.
--Inspect the small hose coming from the water pump (hose mentioned in the video). Clamp this hose at the bottom portion before installing the new thermostat housing as it will help it to not move around.
--The 98" lbs of torque is for both the metal and plastic pieces. However, you can go to 100" lbs for the metal parts if desired.
--When adding coolant, be careful. The coolant flowing to the heater runs through cycles but the thermostat is still closed at first. When the thermostat opens, hot coolant may come out of the reservoir fast. You are able to simply add fluid and tighten the cap. The reservoir is designed to remove the air bubbles but I like to do it the way in the video at first. It is your preference. If you add fluid and close it up, it's good as long as the engine is running well. Just keep the heat on for 15 min. and WATCH THE TEMP. GAUGE FOR OVERHEATING for any process you use.
--Recycle the used coolant because it is toxic. You can call around to various shops to see if they will take it or you can call the city that you are in and ask if they have any place to recycle it.
--Be sure to remove the negative battery connection when disconnecting any electrical components.
By viewing this video you are agreeing that I am not liable for anything, ever.