Coolant system filling and bleeding

[kk2002s]

I used UVeiw but still needed Nose Down, a few drive cycles with Purge up

Question on the Purge Valve behavour ????
I've had it in the non-purge (Latch NOT holding it up) for a few drives, I still have the cover off. I notice the plunger seems to move up a bit after a drive. Then when it cools, the plunger retracts.
Is this normal???
I replaced tank this past December
The car is running much cooler than before WP, low temp Thermo, Flush.