I had done my homework and found these procedures on this great forum.

"Simple technique to purge air from the cooling system. …There are two hoses on the overflow tank. Follow the smaller/upper one until you reach it’s junction point. Remove that connection. Fill the overflow tank and put the cap on tight. Blow into the overflow tank via the line that your removed. This will force coolant from the overflow tank into the cooling system. When the tank is empty, refill and repeat. Continue doing this until fluid begins to exit from the other end of that hose connection you removed. Reinstall hose. DONE! Works like a charm!"

"there is a T fitting with approx 1/2 line right at the top of the radiator in the middle. one hose goes to the coolant res. disconnect it at the t, fill the res, put the cap on tight. put the hose in your mouth and blow into it. refill the res and repeat till you have fluid running out of the t, reconnect, fill res, run engine to full temp, thermo opens, check level and your done"

I followed both procedures and still no joy. After a thermostat change and a road test, the HUD cooling system gauge is maxed out, the DIC say hot engine, no A/C, but the dash gauge reads 100 deg F. Since the dash gauge reads nothing, it sure sounded like a bubble to me, so back to procedures, plus a little.

The plus...disconnected the cooling system hose that tees into the line that connects to the expansion tank top. The one under the air bridge. I removed this rubber line. I attached a "blow line" to the tee and another clear hose to the steel fitting that goes to the top of the engine. That line fed to a capture bottle. I filled and refilled the expansion tank and blew into the tee enough times to have captured 1.5 gallons of coolant without ever getting an air bubble out of the engine. Coolant always, no air.

Upon restart, still no dash gauge reading, HUD at max, DIC saying hot. Suggestions please. I'm standing by. HEEEELLLLLLLP

 

There's another member posting issues (similar?) now on an ongoing thread related to installing a 160* thermostadt. Apparently, tuner omitted/forgot/missed making proper setting. Did you recently change your T to a 160*? If so has it been tuned to reflect the change?

More knowledgable members familiar with the cooling system will be along to offer their .02, I'm sure.
Good luck, might be a PITA/learning expereince, however doesn't 'sound' serious.

 

UPDATE...

Due to the ambiguity of the written procedures (which of the three hoses on a tee are to be disconnected), I disconnected the top line on the expansion tank and ran the hose into a capture tank. Connected a blow hose to the expansion tank fitting and blew til I nearly passed out. No bubbles. No change. Engine runs fine and it is NOT overheating.

I forgot to mention that a Diablotune was also installed. I'm now on my way to checking fan control.

 

I never "burp" my cars, I run them with the radiator/fill cap off until they come up to temp and continue to fill them until they are up the correct level.

If you want to check the fans turn on the AC as it will command the fans.

 

Joy has returned. and I don't even know anyone named Joy, but it's back none-the-less.

Confident that the engine was not overheating, but trying to find out where the fan control stood, I hooked-up my Diablo Predator. I perused around, but decided to not change the Diablotune, so on the way exiting, I had a chance to reinstall the Diablotune and did so. Gauges now normal, no DIC warning, HUD gauge normal, runs good. Really good. Holy crap that feels good. After a road test still all normal. The expansion tank did go down a bit, so perhaps there was a bubble around the sensor(s). In either case, I think it's good to go.

March 12, 60 degrees, sunny, SW Michigan, way above normal. Thanks again to Al Gore for inventing global warming, too.

Futher replies, comments and theories are welcome.

UPDATE 3 Apr 2012:
After reviewing the 160 stat issue and that it might also be causing a closed loop/open loop issue to the ECM, I decided to nix the 160 and return to OEM Stat. Ultimately, the 160 was causing a code to be thrown that indicates conditions of a stuck thermostat. If the engine does not heat to a prescribed temp in a prescribed time...error code with the 160. No error codes now and am in the mid stages of getting a Diablew tune finished out. Holy, crap, the Diablew tune is spectacular.