weird E83 3.0 M54 coolant temperature issue after coolant system overhaul

[mattymic]

I have STF and everywhere else but...

So I replaced the cooling system, everything but the radiator. The temp gauge drops from 12:00 to around 10:00 position and then cycles back up over and over. Replaced the thermostat b/c thought the new one was defective. It didn't do this before the overhaul.

So I used the 7.0 actual Celsius gauge on the dash and watched it during a 40 minute trip into philly. It goes back and forth progressively once it was warmed up between 63 - 74 C. The gauge on the car must move to the middle when it gets above the low end range. When it was parked at the end of the drive and sat running, it moved between 72 and 80.

So it is never getting warmed up? Should be around 100 C right?

Please tell me this isn't the dual temp sensor on the back of the engine? a bad bleed? but I had the mechanic bleed it in case I did it wrong. Another bad thermostat? what are the odds of that?

Maybe I should put my infrared tire temp gauge on the system, to see if it matches up.

Thanks for your help.

[M_3_X]

It seems to me like a bleeding issue.
I've never seen these thermostats but is there a possibility of installing it in the wrong direction?