Thermostat dead... But wait.. What?

So, my thermostat died on me. It's stuck open. No biggie, I can fix that.

But, I noticed, (this is the idiot kid inside me) when I redline the car in 1st and 2nd.. Te temp Hague goes from cold to instant overheat..

If I turn the car off and back on, the temp goes back to an accurate reading of just above the blue.

Wondering if anyone knows why The Hague would JUMP to the farthest point in the red zone like that, if the engine isn't even hot?

Thanks in advance.

Also, no one needs to flame me for redlining the car.. This is my winter beater, (2004 325xi 5spd.) and I understand redline isn't smart but flaming me won't ever make me stop.

Just looking for an explanation as to why it would jump, but once the car is restarted, it'll read accurate again.

You might have an air bubble in the system. Or your coolant temp sensor is wonky.

Would bleeding work to fix te air bubble if there is one?

Yes, bleeding properly would eliminate any air you have on the system.