they are dummy which essentially let you know only when something is already wrong. the temps do fluctuate while the needle stays still but the needle shouldn't spike when temperature is normal, unless something is wrong of course

 

Try bleeding air by disconnecting the throttle body coolant hose from the coolant pipe at the top front of the block.

 

i can almost guarantee its your thermostat...
you should have changed that out before you change the waterpump...
if you still think its your headgasket have a local shop pressurize your cooling system..

 

it was originally leaking air into the system but that was traced to a loose thermostat. once that was tightened, no more air. also, the thermostat was checked and found to be functioning fine. that is why we didn't change it originally. but i guess that was an incorrect assessment. we will see soon. i have only seen temps rise once or twice in the past month or so