Okay, got another mystery. Previously replaced all plastic cooling system parts and installed the aluminum thermostat housing. All was well. The other day I got the check engine temperature message which was backed up by steam from under the hood. Pulled over and had towed home. Okay, no problem bad hose or something. Checked out today. Coolant residual in area of thermostat but started and filled but no leak. Let heat up...no leak. Filled with coolant and bled system. Temperature still exceeding normal. Have been having issue with temperature control last few weeks. In Arizona so run AC all summer. Whenever the temperature spread (inside setting versus outside) is less than 15 degrees or so the passenger side starts blowing warm. So I bump the temperature up to 90 until the left side gets hot and then back down to 65 and passenger gets cool again. That is not working now. The gasket in the thermostat housing seemed a little off so tweaked and reinstalled thought that may have been source of leak. So now it is not overheating or leaking but passenger side is always hot. I know for a fact that it was leaking so why not now...I didn't touch anything when I started and no leak? I heard Joeger say the dccv cannot cause overheating without a leak so what is going on here?!