BLACKJACK -
2 things...
I have yet to see a bleeding problem that resulted in the temp guage acting in a predictable linear fashion....wild swings are the norm, ranging from way hot down to cold - but the needle will always move smoothly. Quickly maybe, but smoothly. It will never snap up and down like a second hand on a fake Rolex.
I have seen many cars that have (usually ground) problems to the dash that result in the temp guages jumping around - and indicating too hot.
Your radiator needs some way to purge it of air.
Pat