E53 Coolant Gauge Dead?

[DIYX5]

Hi Guys, I'm new to the forum. I've been learning a lot from all you experts. Thank you.
I have a 2001 X5 4.4i, E53 with 80K miles.

Radiator hoses burst and instrument panel coolant gauge shot into red.
Pulled car over and took it to indy - 3 miles away.
After investigating, Indy replaced Radiator, fan, cooling pump, hoses, belts thermostat...everything except the coolant tank.. one big job.

Now, the instrument panel coolant gauge does not register the engine temperature, its always blue.
BTW, the HVAC climate control when I set it to Max cold blows only cool air. I set it to Hot, and did not get too hot.

Asked Indy to check again, he did, and says everything is new, could be the instrument panel gauge. I've spent $$$$so far, and would like to tackle this myself. Please advice.