Coolant warning light and jumping gauge

[BHP231]

Hi. 997 series II Carrera.
Couple of times recently the gauge for the coolant is stuck in the low number (40) and not moving. The red light to the right of the gauge comes on as well.
Then the light goes out, the needle jumps to the 60 mark and then jumps to the 80 mark where it should be and seems to right itself.
The whole thing take a couple of minutes and has happened twice in the last 4 or 5 drives.
Before taking it to the Porsche mechanic I wondered if anyone had any thoughts.
Thanks. Andy

[Uwon]

Presume that you are not getting any error codes.
My first guess, low coolant or air pocket in system. I would elevate the rear slightly, open the coolant reservoir, let the motor cool down at least 12 hours overnight. You may have to add some coolant in the morning before closing up the reservoir and starting the engine.
Second guess is a sticky needle. Tap it and see if you get any reaction.
Third guess is a bad or dirty sensor. When was the cooling system last flushed?
Others will, I'm sure, weigh in.
Johan

[BHP231]

Thanks. Tilt and top up seems to have worked.

[BHP231]

So things didn’t work. Car went to the dealer who had it a week and changed the coolant tank sensor, all up $500 spent and the problem is still there.
Seems to happen after taking off and keeps going until temp comes up.
Dealer is researching but so far they have no idea.
Anyone else?
Photo of what this looks like on the dash....